U.S. patent application number 14/399679 was filed with the patent office on 2015-04-30 for method of microbially producing metal gallate spinel nano-objects, and compositions produced thereby.
The applicant listed for this patent is UT-BATTELLE, LLC. Invention is credited to Chad E. Duty, Ilia N. Ivanov, Gerald E. Jellison, JR., Jongsu Kim, Lonnie J. Love, Ji Won Moon, Jehong Park, Tommy J. Phelps.
Application Number | 20150118519 14/399679 |
Document ID | / |
Family ID | 49551128 |
Filed Date | 2015-04-30 |
United States Patent
Application |
20150118519 |
Kind Code |
A1 |
Duty; Chad E. ; et
al. |
April 30, 2015 |
METHOD OF MICROBIALLY PRODUCING METAL GALLATE SPINEL NANO-OBJECTS,
AND COMPOSITIONS PRODUCED THEREBY
Abstract
A method of forming a metal gallate spinel structure that
includes mixing a divalent metal-containing salt and a
gallium-containing salt in solution with fermentative or
thermophilic bacteria. In the process, the bacteria nucleate metal
gallate spinel nano-objects from the divalent metal-containing salt
and the gallium-containing salt without requiring reduction of a
metal in the solution. The metal gallate spinel structures, as well
as light-emitting structures in which they are incorporated, are
also described.
Inventors: |
Duty; Chad E.; (Knoxville,
TN) ; Jellison, JR.; Gerald E.; (Oak Ridge, TN)
; Love; Lonnie J.; (Knoxville, TN) ; Moon; Ji
Won; (Oak Ridge, TN) ; Phelps; Tommy J.;
(Knoxville, TN) ; Ivanov; Ilia N.; (Knoxville,
TN) ; Kim; Jongsu; (Busan, KR) ; Park;
Jehong; (Busan, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UT-BATTELLE, LLC |
Oak Ridge |
TN |
US |
|
|
Family ID: |
49551128 |
Appl. No.: |
14/399679 |
Filed: |
March 14, 2013 |
PCT Filed: |
March 14, 2013 |
PCT NO: |
PCT/US2013/031357 |
371 Date: |
November 7, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61644211 |
May 8, 2012 |
|
|
|
Current U.S.
Class: |
428/690 ;
435/168 |
Current CPC
Class: |
C01P 2002/32 20130101;
C09K 11/642 20130101; C30B 29/26 20130101; C01P 2002/52 20130101;
C09K 11/682 20130101; C09K 11/621 20130101; C09K 11/65 20130101;
C09K 11/623 20130101; C01P 2002/72 20130101; C09K 11/7702 20130101;
C01G 15/00 20130101; H01L 33/504 20130101; C09K 11/773 20130101;
C01G 15/006 20130101; C09K 11/7728 20130101; C12P 3/00 20130101;
C01P 2002/84 20130101 |
Class at
Publication: |
428/690 ;
435/168 |
International
Class: |
C09K 11/77 20060101
C09K011/77; C12P 3/00 20060101 C12P003/00 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] This invention was made with government support under
Contract Number DE-AC05-00OR22725 between the United States
Department of Energy and UT-Battelle, LLC. The U.S. government has
certain rights in this invention.
Claims
1. A method of forming a metal gallate spinel structure, the method
comprising: providing a supply of fermentative or thermophilic
bacteria; reacting a divalent metal-containing salt and a
gallium-containing salt with the supply of fermentative or
thermophilic bacteria, wherein treatment of the divalent
metal-containing salt and the gallium-containing salt with the
fermentative or thermophilic bacteria nucleates a divalent metal
gallate spinel structure.
2. The method of claim 1, further comprising doping the divalent
metal gallate spinel structure with at least one dopant to tune a
wavelength of light emission from the divalent metal gallate spinel
structure.
3. The method of claim 1, wherein the fermentative or thermophilic
bacteria comprises Thermoanerobacter bacteria, Thermoanerobium
bacteria, or a combination thereof.
4. The method of claim 1, wherein the divalent metal-containing
salt, the gallium-containing salt and the supply of fermentative or
thermophilic bacteria are contained in an aqueous solution.
5. The method of claim 1, wherein a zinc gallate spinel structure
is formed by selecting the divalent metal-containing salt as a
zinc-containing salt, wherein treatment of the zinc-containing salt
and the gallium-containing salt with the fermentative or
thermophilic bacteria nucleates a zinc gallate spinel
structure.
6. The method of claim 5, further comprising doping the zinc
gallate spinel structure with at least one dopant to tune a
wavelength of light emission from the zinc gallate spinel
structure.
7. The method of claim 5, wherein the zinc-containing salt is
selected from zinc chloride (ZnCl.sub.2), zinc bromide
(ZnBr.sub.2), zinc nitrate hydrate (Zn(NO.sub.3).sub.2.xH.sub.2O),
zinc sulfate hydrate (ZnSO.sub.4.xH.sub.2O), zinc phosphate
(Zn.sub.3(PO.sub.4).sub.2), zinc acetate hydrate
((CH.sub.3CO.sub.2).sub.2Zn).xH.sub.2O), zinc stearate
([CH.sub.3(CH.sub.2).sub.16COO].sub.2Zn), zinc fluoride
(ZnF.sub.2), zinc iodide (ZnI.sub.2), zinc methoxide
(C.sub.2H.sub.6O.sub.2Zn), zinc acrylate
((H.sub.2C.dbd.CHCO.sub.2).sub.2Zn), and combinations thereof.
8. The method of claim 1, wherein the gallium-containing salt is
selected from gallium chloride (GaCl.sub.3), gallium chloride
(GaCl.sub.2), gallium nitrate hydroxide (GaNO.sub.3.xH.sub.2O),
gallium fluoride (GaF.sub.3), gallium iodide (GaI.sub.3), gallium
bromide (GaBr.sub.3), gallium sulfate hydrate
(GaSO.sub.4.xH.sub.2O), and combinations thereof.
9. The method of claim 5, wherein the zinc gallate spinel structure
comprises ZnGa.sub.2O.sub.4.
10. The method of claim 1, wherein the treatment of the divalent
metal-containing salt and the gallium-containing salt with the
fermentative or thermophilic bacteria to nucleate the divalent
metal gallate spinel structure comprises adjusting a pH of a
solution of the divalent metal-containing salt, the
gallium-containing salt, and the fermentative or thermophilic
bacteria within a range of 5.5 to 8.5.
11. The method of claim 1, wherein the treatment of the divalent
metal-containing salt and the gallium-containing salt with the
fermentative or thermophilic bacteria to nucleate the divalent
metal gallate spinel structure comprises adjusting an E.sub.h of a
solution of the divalent metal-containing salt, the
gallium-containing salt, and the thermophilic bacteria within a
range of 100 mV to -350 mV.
12. The method of claim 5, wherein the zinc gallate spinel
structure is a blue phosphor.
13. The method of claim 2, wherein the dopant is at least one
selected from the group consisting of Mn, Cr, Eu, Co, Dy, and
combinations thereof.
14. The method of claim 6, wherein the doping of the zinc gallate
spinel comprises Co.sup.2+ dopant and the wavelength of light
emission ranges from 400 nm to 495 nm.
15. The method of claim 6, wherein the zinc gallate spinel is doped
with Mn.sup.2+ dopant and the wavelength of light emission ranges
from 495 nm to 570 nm.
16. The method of claim 15, wherein doping of the zinc gallate
spinel structure with Mn.sup.2+ comprises mixing the zinc gallate
spinel structure with a manganese salt selected from manganese
chloride hydrate(MnCl.sub.2.xH.sub.2O), manganese nitrate hydrate
(Mn(NO.sub.3).sub.2.xH.sub.2O), manganese sulfate hydrate
(MnSO.sub.4.xH.sub.2O), manganese iodide (MnI.sub.2), manganese
bromide (MnBr.sub.2), manganese fluoride (MnF.sub.3), manganese
acetate hydrate (Mn(CH.sub.3COO).sub.2.xH.sub.2O), and manganese
carbonate (MnCO.sub.3).
17. The method of claim 6, wherein the zinc gallate spinel is doped
with Cr.sup.3+ or Eu.sup.3+ and the wavelength of light emission
ranges from 570 nm to 750 nm.
18. The method of claim 17, wherein doping of the zinc gallate
spinel structure with Cr.sup.3+ comprises mixing the zinc gallate
spinel structure with a chromium salt selected from chromium
chloride hydrate (CrCl.sub.3.xH.sub.2O), chromium nitrate hydrate
(Cr(NO.sub.3).sub.3.xH.sub.2O), chromium acetate hydroxide
((CH.sub.3CO.sub.2).sub.7Cr.sub.3(OH).sub.2), chromium sulfate
hydrate (Cr.sub.2(SO.sub.4).sub.3.xH.sub.2O), chromium fluoride
hydrate (GaF.sub.3.xH.sub.2O), chromium iodide hydrate
(GaI.sub.3.xH.sub.2O), chromium bromide hydrate
(GaBr.sub.3.xH.sub.2O), chromium phosphate hydrate
(Cr(PO.sub.4).xH.sub.2O), and combinations thereof.
19. The method of claim 17, wherein doping of the zinc gallate
spinel structure with Eu.sup.3+ comprises mixing the zinc gallate
spinel structure with a europium salt selected from europium
chloride hydrate (EuCl.sub.3.xH.sub.2O), europium fluoride hydrate
(EuF.sub.3.xH.sub.2O), europium nitrate hydrate
(Eu(NO.sub.3).sub.3.xH.sub.2O), europium acetate hydroxide
((CH.sub.3CO.sub.2).sub.7Eu.sub.3(OH).sub.2), europium bromide
hydrate (EuBr.sub.3.xH.sub.2O), europium sulfate hydrate
(Eu.sub.2(SO.sub.4).sub.3.xH.sub.2O), and combinations thereof.
20. The method of claim 6, wherein the zinc gallate spinel is doped
with Dy.sup.3+ dopant and the wavelength of light emission is in a
wavelength ranging from 450 nm to 510 nm, or a wavelength ranging
from 560 nm to 610 nm, or a wavelength ranging from 660 nm to 720
nm, or a wavelength ranging from 755 nm to 810 nm.
21. The method of claim 20, wherein doping the zinc gallate spinel
structure with Dy.sup.3+ comprises mixing the zinc gallate spinel
structure with a dysprosium salt selected from dysprosium chloride
hydrate (DyCl.sub.3.xH.sub.2O), dysprosium fluoride hydrate
(DyF.sub.3.xH.sub.2O), dysprosium nitrate hydrate
(Dy(NO.sub.3).sub.3.xH.sub.2O), dysprosium acetate hydroxide
((CH.sub.3CO.sub.2).sub.7Dy.sub.3(OH).sub.2), dysprosium bromide
hydrate (DyBr.sub.3.xH.sub.2O), dysprosium sulfate hydrate
(Dy.sub.2(SO.sub.4).sub.3.xH.sub.2O), and combinations thereof.
22. The method of claim 2, further comprising annealing of the
divalent metal gallate spinel after being doped with a dopant
selected from the group consisting of Mn, Cr, Eu, Dy, and
combinations thereof.
23. The method of claim 22, wherein the annealing of the divalent
metal gallate spinel is conducted at a temperature ranging from
800.degree. C. to 1000.degree. C. for a time ranging from 15
minutes to 2 hours.
24. The method of claim 1, wherein reacting of the divalent
metal-containing salt and the gallium-containing salt with the
supply of fermentative or thermophilic bacteria is conducted at a
temperature ranging from 45.degree. C. to 105.degree. C.
25. The method of claim 1, wherein the divalent metal gallate
spinel structure produces white light.
26. A method of forming a structure for emitting white light, the
method comprising: forming a first phosphor of a first doped zinc
gallate spinel structure that is nucleated by a first fermentation
with a first thermophilic bacteria and first annealing, wherein the
first phosphor emits a first wavelength of red light ranging from
620 nm to 750 nm; forming a second phosphor of a second doped zinc
gallate spinel structure that is nucleated by a second fermentation
with a second thermophilic bacteria and a second annealing, wherein
the second phosphor emits a wavelength of green light ranging from
495 nm to 570 nm; forming a third phosphor of a second zinc gallate
spinel structure that is nucleated by a third fermentation with a
third thermophilic bacteria, wherein the third phosphor emits a
wavelength of blue light ranging from 400 nm to 495 nm; and mixing
at least the first phosphor, second phosphor and third phosphor to
form the structure for emitting the white light.
27. The method of claim 26, wherein at least one of the first
annealing and second annealing for forming the first phosphor, the
second phosphor or the third phosphor comprises sintering at a
temperature ranging from 800.degree. C. to 1000.degree. C. for a
time ranging from 15 minutes to 2 hours.
28. The method of claim 26, wherein at least one of the first doped
zinc gallate spinel structure, the second doped zinc gallate spinel
structure, and the third doped zinc gallate structure comprises a
zinc gallate that is nucleated from a mixture of a zinc-containing
salt and a gallium-containing salt in the presence of the
thermophilic bacteria, wherein reaction between the zinc-containing
salt and the gallium-containing salt is not a reduction type
reaction.
29. The method of claim 26, wherein the zinc-containing salt is
selected from zinc chloride (ZnCl.sub.2), zinc bromide
(ZnBr.sub.2), zinc nitrate hydrate (Zn(NO.sub.3).sub.2.xH.sub.2O),
zinc sulfate hydrate (ZnSO.sub.4.xH.sub.2O), zinc phosphate
(Zn.sub.3(PO.sub.4).sub.2), zinc acetate hydrate
((CH.sub.3CO.sub.2).sub.2Zn).xH.sub.2O), zinc stearate
([CH.sub.3(CH.sub.2).sub.16COO].sub.2Zn), zinc fluoride
(ZnF.sub.2), zinc iodide (ZnI.sub.2), zinc methoxide
(C.sub.2H.sub.6O.sub.2Zn), zinc acrylate
((H.sub.2C.dbd.CHCO.sub.2).sub.2Zn), or combinations thereof, and
the gallium-containing salt comprises gallium chloride
(GaCl.sub.3), gallium chloride (GaCl.sub.2), gallium nitrate
hydroxide (GaNO.sub.3.xH.sub.2O), gallium fluoride (GaF.sub.3),
gallium iodide (GaI.sub.3), gallium bromide (GaBr.sub.3), gallium
sulfate hydrate (GaSO.sub.4.xH.sub.2O), and combinations
thereof.
30. The method of claim 26, wherein the second doped zinc gallate
spinel structure is doped with Mn.sup.2+ dopant, wherein the
Mn.sup.2+ dopant is introduced to the zinc gallate by mixing the
zinc gallate spinel structure with a manganese salt selected from
manganese chloride hydrate(MnCl.sub.2.xH.sub.2O), manganese nitrate
hydrate (Mn(NO.sub.3).sub.2.xH.sub.2O), manganese sulfate hydrate
(MnSO.sub.4.xH.sub.2O), manganese iodide (MnI.sub.2), manganese
bromide (MnBr.sub.2), manganese fluoride (MnF.sub.3), manganese
acetate hydrate (Mn(CH.sub.3COO).sub.2.xH.sub.2O), and manganese
carbonate (MnCO.sub.3), and combinations thereof.
31. The method of claim 26, wherein the first doped zinc gallate
spinel structure is doped with Cr.sup.3+ dopant, wherein the
Cr.sup.3+ dopant is introduced to the first doped zinc gallate
spinel structure dopant by mixing the zinc gallate with a chromium
salt selected from chromium chloride hydrate
(CrCl.sub.3.xH.sub.2O), chromium nitrate hydrate
(Cr(NO.sub.3).sub.3.xH.sub.2O), chromium acetate hydroxide
((CH.sub.3CO.sub.2).sub.7Cr.sub.3(OH).sub.2), chromium sulfate
hydrate (Cr.sub.2(SO.sub.4).sub.3.xH.sub.2O), chromium fluoride
hydrate (GaF.sub.3.xH.sub.2O), chromium iodide hydrate
(GaI.sub.3.xH.sub.2O), chromium bromide hydrate
(GaBr.sub.3.xH.sub.2O), chromium phosphate hydrate
(Cr(PO.sub.4).xH.sub.2O), and combinations thereof.
32. The method of claim 26, wherein the first doped zinc gallate
spinel structure is doped with Eu.sup.+ dopant, wherein the
Eu.sup.3+ dopant is introduced to the first doped zinc gallate
spinel structure dopant by mixing the zinc gallate with a europium
salt selected from europium chloride hydrate
(EuCl.sub.3.xH.sub.2O), europium fluoride hydrate
(EuF.sub.3.xH.sub.2O), europium nitrate hydrate
(Eu(NO.sub.3).sub.3.xH.sub.2O), europium acetate hydroxide
((CH.sub.3CO.sub.2).sub.7Eu.sub.3(OH).sub.2), europium bromide
hydrate (EuBr.sub.3.xH.sub.2O), europium sulfate hydrate
(Eu.sub.2(SO.sub.4).sub.3.xH.sub.2O), and combinations thereof.
33. The method of claim 28 further comprising forming a fourth
phosphor of a fourth doped zinc gallate spinel structure with
Dy.sup.3+ dopant and the wavelength of light emission for the
fourth doped zinc gallate spinel is in a wavelength ranging from
450 nm to 510 nm, or a wavelength ranging from 560 nm to 610 nm, or
a wavelength ranging from 660 nm to 720 nm or a wavelength ranging
from 755 nm to 810 nm.
34. The method of claim 33, wherein doping of the zinc gallate
spinel structure with Dy.sup.3+ comprises mixing the zinc gallate
spinel structure with a dysprosium salt selected from dysprosium
chloride hydrate (DyCl.sub.3.xH.sub.2O), dysprosium fluoride
hydrate (DyF.sub.3.xH.sub.2O), dysprosium nitrate hydrate
(Dy(NO.sub.3).sub.3.xH.sub.2O), dysprosium acetate hydroxide
((CH.sub.3CO.sub.2).sub.7Dy.sub.3(OH).sub.2), dysprosium bromide
hydrate (DyBr.sub.3.xH.sub.2O), dysprosium sulfate hydrate
(Dy.sub.2(SO.sub.4).sub.3.xH.sub.2O), and combinations thereof.
35. A white light emitting structure comprising: a first zinc
gallate spinel doped with chromium or europium that provides a red
light emitting phosphor; a second zinc gallate spinel doped with
manganese that provides a green light emitting phosphor; a third
zinc gallate spinel that provides a blue light emitting phosphor;
and a transparent substrate, wherein the first zinc gallate spinel,
the second zinc gallate spinel, and the third zinc gallate spinel
are distributed on the transparent substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority from U.S.
Provisional Application No. 61/644,211, filed on May 8, 2012, which
is herein incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0003] The present disclosure relates to luminescent materials, and
more particularly relates to the production of luminescent
materials using fermentation type processes.
BACKGROUND
[0004] Conventional incandescent bulb design is not energy
efficient. In some instances, 98% of the energy input to
incandescent bulbs ends up as heat instead of light. Energy
conversion to visible light for fluorescent lighting technology is
much higher, e.g., 10% to 15%. However, their design requires
mercury, which is toxic to the environment, thereby posing a
problem for recycling of these lamps. Thus, there are ongoing
efforts in finding new materials having luminescent and
phosphorescent properties that can be more environmentally friendly
while remaining cost effective and amenable to scaled up
production.
SUMMARY OF THE INVENTION
[0005] In one embodiment of the present disclosure, a metal gallate
spinel structure is provided by mixing a divalent metal-containing
salt (e.g., salt of Cu.sup.+2, Zn.sup.+2, or Cd.sup.+2) with a
gallium-containing salt in solution with fermentative or
thermophilic bacteria under conditions where the bacteria nucleate
and grow the divalent metal gallate spinel structure. In particular
embodiments, a zinc gallate spinel structure is provided by mixing
a zinc-containing salt and a gallium-containing salt in solution
with fermentative or thermophilic bacteria under conditions where
the bacteria nucleate and grow the zinc gallate spinel structure.
The bacteria nucleates a metal gallate spinel structure from the
metal-containing salt and the gallium-containing salt without
requiring reduction of at least a metal from the mixed salt
solution.
[0006] In another aspect of the present disclosure, a method of
forming a divalent metal gallate spinel structure is provided in
which the divalent metal gallate spinel structure is doped to tune
an emission wavelength that is provided by the doped divalent metal
gallate spinel. In one embodiment, the method of forming the
divalent metal gallate spinel structure includes providing a supply
of fermentative or thermophilic bacteria and reacting a
metal-containing salt and a gallium-containing salt with the supply
of bacteria. Treatment of the divalent metal-containing salt and
the gallium-containing salt with the thermophilic bacteria
nucleates a divalent metal gallate spinel structure. The metal
gallate spinel (and particularly, zinc gallate spinel) structure
may be doped to tune a wavelength of light emission from the metal
gallate spinel structure. The metal gallate spinel structure may
then be annealed.
[0007] In another aspect of the present disclosure, a method of
forming a structure for emitting white light is provided from doped
phosphors produced by fermentation of metal-containing salts and
gallium-containing salts with fermentative or thermophilic
bacteria. In one particular embodiment, the method of forming a
white light emitting structure includes forming a first phosphor of
a first doped metal gallate spinel (particularly, zinc gallate
spinel) structure that is nucleated by a first fermentation with a
fermentative or thermophilic bacteria and annealing. The first
phosphor emits a first wavelength of red light ranging from 570 nm
to 750 nm. A second phosphor of a second doped metal gallate spinel
(particularly, zinc gallate spinel) structure may be nucleated
during a second fermentation with fermentative or thermophilic
bacteria. Following nucleation, the second doped metal gallate
spinel (particularly, zinc gallate spinel) structure may be
annealed, wherein the second doped metal gallate spinel
(particularly, zinc gallate spinel) structure emits a wavelength of
green light ranging from 495 nm to 570 nm. A third phosphor of a
third metal gallate spinel (particularly, zinc gallate spinel)
structure may then be nucleated by a third fermentation with the
fermentative or thermophilic bacteria and may be annealed, in which
the third phosphor emits a wavelength of violet and blue light
ranging from 400 nm to 495 nm. At least the first phosphor, the
second phosphor, and the third phosphor may then be mixed to form
the structure for emitting the white light.
[0008] In yet another aspect of the present disclosure, a white
light emitting structure is provided that is composed of a mixture
of at least three metal gallate spinel (and particularly, zinc
gallate spinel) structures. A first metal gallate spinel (and
particularly, zinc gallate spinel) that is doped with chromium or
europium provides a red light emitting phosphor. A second metal
gallate spinel (and particularly, zinc gallate spinel) that is
doped with manganese provides a green light emitting phosphor. A
third metal gallate spinel (and particularly, zinc gallate spinel)
provides a blue light emitting phosphor. The first, second, and
third phosphor are homogeneously distributed on a transparent
substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The following detailed description, given by way of example
and not intended to limit the disclosure solely thereto, will best
be appreciated in conjunction with the accompanying drawings,
wherein like reference numerals denote like elements and parts, in
which:
[0010] FIG. 1A is a process diagram illustrating a method of
nucleating a zinc gallate spinel structure with fermentative or
thermophilic bacteria without requiring reduction of at least a
metal-containing salt, in accordance with one embodiment of the
present disclosure.
[0011] FIG. 1B is a process diagram illustrating one embodiment of
providing the bacterial broth of step 5 of the process diagram
depicted in FIG. 1A.
[0012] FIG. 2 is a side cross-sectional schematic view of a batch
type reactor used for nucleating a zinc gallate spinel structure
with fermentative or thermophilic bacteria, in accordance with the
present disclosure.
[0013] FIG. 3 is a side cross-sectional schematic view of a
continuous type reactor used for nucleating a zinc gallate spinel
structure with fermentative or thermophilic bacteria, in accordance
with the present disclosure.
[0014] FIG. 4 is a process diagram illustrating a method of forming
doped zinc gallate spinel structures with fermentative or
thermophilic bacteria, in accordance with one embodiment of the
present disclosure.
[0015] FIG. 5 is a perspective view of a structure for emitting
white light from doped phosphors produced by fermentation of
zinc-containing salts and gallium-containing salts with
thermophilic bacteria and tuned by dopants, in accordance with one
embodiment of the present disclosure.
[0016] FIG. 6 is a plot of the fluorescence from one example of a
pure zinc gallate spinel structure that was formed in accordance
with the present disclosure.
[0017] FIG. 7 is an X-ray diffraction pattern of one example of
pure zinc gallate spinel structure that was formed in accordance
with the present disclosure.
[0018] FIG. 8 depicts X-ray diffraction patterns for zinc gallate
spinel structures that have been doped with cobalt, in accordance
with one embodiment of the present disclosure.
[0019] FIG. 9 is a plot of the fluorescence from zinc gallate
spinel structure doped with cobalt in response to the application
of ultraviolet light having a wavelength of 254 nm, in which the
cobalt doped zinc gallate spinel structures were doped in
accordance with the present disclosure.
[0020] FIG. 10 is a plot of the fluorescence from zinc gallate
spinel structure doped with cobalt in response to the application
of ultraviolet light having a wavelength of 288 nm, in which the
cobalt doped zinc gallate spinel structures were doped in
accordance with the present disclosure.
[0021] FIG. 11 depicts X-ray diffraction patterns for zinc gallate
spinel structures that have been doped with manganese, in which the
manganese is a substitutional dopant with zinc in the doped zinc
gallate spinel structure, in accordance with one embodiment of the
present disclosure.
[0022] FIG. 12 is a plot of the fluorescence from zinc gallate
spinel structure doped with manganese in response to the
application of ultraviolet light having a wavelength of 288 nm, in
which the manganese is a substitutional dopant for the zinc in the
zinc gallate spinel structure, in accordance with one embodiment of
the present disclosure.
[0023] FIG. 13 depicts X-ray diffraction patterns for zinc gallate
spinel structures that have been doped with manganese, in which the
manganese is a substitutional dopant with gallium in the doped zinc
gallate spinel structure, in accordance with one embodiment of the
present disclosure.
[0024] FIG. 14 is a plot of the fluorescence from zinc gallate
spinel structure doped with manganese in response to the
application of ultraviolet light having a wavelength of 288 nm, in
which the manganese is a substitutional dopant for the gallium in
the zinc gallate spinel structure, in accordance with one
embodiment of the present disclosure.
[0025] FIG. 15 depicts X-ray diffraction patterns for zinc gallate
spinel structures that have been doped with chromium, in which the
chromium is a substitutional dopant with gallium in the doped zinc
gallate spinel structure, in accordance with one embodiment of the
present disclosure.
[0026] FIG. 16 is a plot of the fluorescence from zinc gallate
spinel structure doped with chromium in response to the application
of ultraviolet light having a wavelength of 288 nm, in which the
chromium is a substitutional dopant for the gallium in the zinc
gallate spinel structure, in accordance with one embodiment of the
present disclosure.
[0027] FIG. 17 depicts X-ray diffraction patterns for zinc gallate
spinel structures that have been doped with europium, in which the
europium is a substitutional dopant with gallium in the doped zinc
gallate spinel structure, in accordance with one embodiment of the
present disclosure.
[0028] FIG. 18 is a plot of the fluorescence from zinc gallate
spinel structure doped with europium in response to the application
of ultraviolet light having a wavelength of 288 nm, in which the
europium is a substitutional dopant for the gallium in the zinc
gallate spinel structure, in accordance with one embodiment of the
present disclosure.
[0029] FIG. 19 is a plot of the fluorescence from a mixture of
doped zinc gallate spinel in response to the application of
ultraviolet light having a wavelength of 254 nm, in accordance with
one embodiment of the present disclosure.
[0030] FIG. 20 shows an X-ray diffraction pattern for copper
gallate spinel structures produced by the microbial method
described herein.
DETAILED DESCRIPTION
[0031] Detailed embodiments of the present disclosure are described
herein; however, it is to be understood that the disclosed
embodiments are merely illustrative of the compositions, structures
and methods of the disclosure that may be embodied in various
forms. In addition, the examples given in connection with the
various embodiments are intended to be illustrative, and not
restrictive. Further, the figures are not necessarily to scale,
some features may be exaggerated to show details of particular
components. Therefore, specific structural and functional details
disclosed herein are not to be interpreted as limiting, but merely
as a representative basis for teaching one skilled in the art to
variously employ the compositions, structures and methods disclosed
herein. References in the specification to "one embodiment", "an
embodiment", "an example embodiment", etc., indicate that the
embodiment described may include a particular feature, structure,
or characteristic, but every embodiment may not necessarily include
the particular feature, structure, or characteristic. Moreover,
such phrases are not necessarily referring to the same
embodiment.
[0032] Referring to FIG. 1, in one embodiment, the present
disclosure provides a method of nucleating divalent metal
(particularly zinc) gallate spinel structures from divalent
metal-containing salts and gallium-containing salts with
fermentative or thermophilic bacteria. The method disclosed herein
may be referred to as nanofermentation of the divalent metal
gallate spinel structures. Nanofermentation is a process of
microbially induced, i.e., induced by fermentative or thermophilic
bacteria, using microbial activity as the driving force for
nucleating divalent metal gallate spinel structures on or adjacent
to the cell wall of the fermentative or thermophilic bacteria by
adjusting the pH and reduction potential (E.sub.h) of the micro
environment adjacent to the fermentative or thermophilic
bacteria.
[0033] A spinel structure is a mineral of the formula
A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2-, which crystallizes in the
cubic (isometric) crystal system, with the oxide anions arranged in
a cubic close-packed lattice and the cations A and B occupying some
or all of the tetrahedral and octahedral sites in the lattice. In
general, A and B can be divalent, trivalent, or quadrivalent
cations. In the divalent metal gallate structures considered
herein, A can be any divalent metal species, and B is Ga.sup.3+.
The divalent metal species can be, for example, an alkaline earth
metal (e.g., Mg.sup.2+, Ca.sup.2+, Sr.sup.2+, or Ba.sup.2+, or a
combination thereof) or a transition metal (e.g., Mn.sup.2+,
Fe.sup.2+, Co.sup.2+, Ni.sup.2+, Cu.sup.2+, Zn.sup.2+, or
Cd.sup.2+, or a combination thereof).
[0034] In some embodiments of the divalent metal gallate structure
A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2-, A contains two or more
divalent metal species (which may be denoted as A and A'), such as
any two of the exemplary divalent metal species provided above. In
such compositions, the divalent metal gallate structure could have
the generic formula A.sub.xA'.sub.1-xGaO.sub.4, wherein A' is
selected from any of the divalent metals provided for A, and the
subscript x is greater than 0 and less than 1, e.g., 0.01, 0.02,
0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 0.98, or
0.99, or a value within a range bounded by any two of the foregoing
values. Some examples of such compositions include the sub-generic
formulas Zn.sub.xCu.sub.1-xGaO.sub.4, Zn.sub.xCd.sub.1-xGaO.sub.4,
Cu.sub.xCd.sub.1-xGaO.sub.4, Sr.sub.xZn.sub.1-xGaO.sub.4,
Sr.sub.xCu.sub.1-xGaO.sub.4, Sr.sub.xCd.sub.1-xGaO.sub.4, and
Ba.sub.xSr.sub.1-xGaO.sub.4, wherein possible values for x have
been provided above.
[0035] In some embodiments, A includes only divalent metal species,
as described above. In other embodiments, A may include, in
addition to one or more divalent metals, one or more monovalent
metals and/or one or more trivalent metals. Some examples of
monovalent metals include the alkali metals (e.g., Li.sup.+,
Na.sup.+, K.sup.+, Rb.sup.+, and Cs.sup.+) as well as some
transition and main groups metals (e.g., Cu.sup.+, Ag.sup.+, and
Tl.sup.+). Some examples of trivalent metals include the main group
metals (e.g., B.sup.3+, Al.sup.3+, Ga.sup.3+, In.sup.3+, As.sup.3+,
Sb.sup.3+, and Bi.sup.3+), transition metals (e.g., Sc.sup.3+,
V.sup.3+, Cr.sup.3+, Mn.sup.3+, Fe.sup.3+, Co.sup.3+, Ni.sup.3+,
and Y.sup.3+), and lanthanide metals (e.g., La.sup.3+, Ce.sup.3+,
Pr.sup.3+, Sm.sup.3+, Eu.sup.3+, Gd.sup.3+, Tb.sup.3+, and
Dy.sup.3+). In the case where monovalent and/or trivalent metals
are included, A and A' in the generic or specific gallate spinel
compositions above can be independently selected from one or more
monovalent, divalent, and trivalent metals, provided that A
contains at least one divalent metal. Some examples of metal
gallate compositions that include either a monovalent or trivalent
metal include Li.sub.0.05Zn.sub.0.975Ga.sub.2O.sub.4,
Al.sub.0.01Zn.sub.0.985Ga.sub.2O.sub.4, and
Cu.sup.+.sub.0.05Cu.sup.2+.sub.0.975Ga.sub.2O.sub.4. In some
embodiments, any of the foregoing monovalent and/or trivalent
metals may be included as dopants into the metal gallate
structure.
[0036] The metal gallate (and particularly, zinc gallate) spinel
structures that are formed in accordance with the present
disclosure are nucleated in a solution with fermentative or
thermophilic bacteria and are not produced by reduction reactions.
In some embodiments, microbial reduction (decrease redox potential)
is employed to achieve the appropriate pH-E.sub.h regime suitable
spinel structure formation, such as zinc gallate phosphor
structures. The term "nucleation", "nucleating", and "nucleate" as
used herein to describe the formation of spinel structures mean
that solute molecules dispersed in a solvent gather into clusters,
on the nanometer scale (elevating solute concentration in a small
region) and become stable. These stable clusters constitute the
nuclei. When the clusters are not stable, they redissolve. The
nucelation of the divalent metal gallate spinel structures in the
solution of fermentative or thermophilic bacteria that are
disclosed herein does not require the reduction of any metal and
non-metal components in the target nanoparticles.
[0037] Redox (reduction-oxidation) reactions describe all chemical
reactions in which atoms have their oxidation state changed. A
"reduction reaction" is the gain of electrons or a decrease in
oxidation state by a molecule, atom, or ion. One example of a
redution reaction is the formation of magnetite spinel
(Fe.sub.3O.sub.4) as in the following reaction:
3Fe.sup.3+O(OH)+1/2H.sub.2.fwdarw.Fe.sup.2+Fe.sup.3+.sub.2O.sub.4+2H.sub-
.2O
In the above reaction, Fe(III) is reduced to Fe(II). Another
example of a reduction reaction is the formation of semiconducting
material (CdS) as in the following reaction:
2Cd.sup.2++S.sub.2O.sub.3.sup.2-+3H.sub.2+2e-.fwdarw.2CdS+3H.sub.2O
In the above reaction S(IV) is reduced to S(-II). In comparison to
the above example of a reduction reaction, the zinc gallate spinel
structure produced using the thermophilic bacteria of the present
disclosure does not include reduction of a metal ion, e.g., Zn. For
example, a zinc gallate structure nucleated at neutral pH in
accordance with the present disclosure may be as follows:
Zn.sup.2++2Ga.sup.3+O(OH)+3H.sub.2+2e.sup.-.fwdarw.Zn.sup.2+Ga.sup.3+.su-
b.2O.sub.4+4H.sub.2O
[0038] Referring to FIG. 1A, in one embodiment, the method of
nucleating metal gallate (and particularly, zinc gallate) spinel
structures may begin at step 5 with providing fermentative or
thermophilic bacterial broth. The term "fermentative bacteria", as
used herein, refers to bacteria that obtain electrons from an
electron donor (e.g. glucose) and then release electrons
extracellularly, thereby resulting in the production of carbon
dioxide, alcohol, and organic acids under anaerobic conditions. The
term "thermophilic bacteria", as used herein, refers to bacteria
that survive at temperatures above 45.degree. C. (113.degree. F.).
In some examples, thermophilic bacteria live at or even above the
boiling point of water. Strains of thermophilic bacteria have been
identified with optimum temperatures ranging from 55.degree. C. to
105.degree. C. (above the boiling point of water), and many
temperatures in between. Thermophilic bacteria occur naturally in
hot springs, tropical soils, compost heaps, etc. In one embodiment,
step 5 the bacterial broth that is depicted in FIG. 1A may include
the steps of the process sequence that is depicted in FIG. 1B. FIG.
1B illustrates that forming the fermentative or thermophilic
bacteria may include the steps of providing a bacterial stock 5a,
providing a biological medium 5b and providing a nutrient, e.g.,
glucose 5c. The fermentative or thermophilic bacteria considered
herein are primarily those that can adjust the microenvironment
around the cell to lower the E.sub.h (e.g., to -100 mV, -200 mV,
-300 mV, or -350 mV), and that preferably survive or thrive around
neutral pH (e.g., 4-10). The bacteria are also preferably less
prone to inactivation from metal toxicity under high metal
concentrations. In some embodiments, the bacteria are both
fermentative and thermophilic, i.e., "fermentative thermophilic
bacteria".
[0039] In one embodiment, the bacterial stock may be a species of
Thermoanaerobacter bacteria. A particular species of
Thermoanaerobacter considered herein is Thermoanaerobacter strain
TOR-39, a sample of which was deposited with the American Type
Culture Collection (10801 University Blvd., Manassas, Va. 20010) on
Sep. 7, 2001 as accession number PTA-3695. Strain TOR-39 is a
thermophile that grows optimally at temperatures from 60.degree. C.
to 70.degree. C. The conditions needed to grow and maintain this
strain, including basal medium, nutrients, vitamins, and trace
elements are detailed in U.S. Pat. No. 6,444,453, the entire
contents of which are incorporated herein by reference. Some
particular strains of Thermoanaerobacter ethanolicus particularly
considered herein include T. ethanolicus strain C1 and T.
ethanolicus strain M3. Some other bacterial species of this class
include Thermoanaerobacter X513, X514, and X561 (as described in
Roh et al., Applied and Environmental Microbiology, December 2002,
pp. 6013-6020) and Thermoanaerobacter OB47 (Hamilton-Brehm et al.,
Applied and Environmental Microbiology, February 2010, pp.
1014-1020).
[0040] Another group of bacteria particularly considered herein is
the class Thermococci. An order of Thermococci particularly
considered herein is Thermococcales. A family of Thermococcales
particularly considered herein is Thermococcaceae. A genus of
Thermococcaceae particularly considered herein is Thermococcus. A
species of Thermococcus particularly considered herein is
Thermococcus litoralis.
[0041] Another group of bacteria particularly considered herein is
the genus Thermoterrabacterium. A species of Thermoterrabacterium
particularly considered herein is Thermoterrabacterium
ferrireducens, and particularly, strain JW/AS-Y7.
[0042] Still another group of bacteria particularly considered
herein is the phylum Deinococcus-Thermus. A class of
Deinococcus-Thermus particularly considered herein is Deinococci.
An order of Deinococci particularly considered herein is Thermales.
A genus of Thermales particularly considered herein is Thermus. A
species of Thermus particularly considered herein is Thermus sp.
strain SA-01.
[0043] Other bacteria particularly considered herein include
thermophilic species within any of the genera Thermoanaerobacterium
(e.g., T. thermosulfurigenes, T. polysaccharolyticum, T. zeae, T.
aciditolerans, and T. aotearoense), Bacillus (e.g., B. infernus),
Clostridium (e.g., C. thermocellum), Anaerocellum (e.g., A.
thermophilum), Dictyoglomus (e.g., D. thermophilum), and
Caldicellulosiruptor (e.g., C. acetigenus, C. hydrothermalis, C.
kristjanssonii, C. kronotskiensis, C. lactoaceticus, C. owensensis,
and C. saccharolyticus).
[0044] It is noted that the above examples of fermentative or
thermophilic bacteria are provided for illustrative purposes only
and are not intended to limit the present disclosure to only the
types of bacteria that are described above. For example,
embodiments have been contemplated in which the bacteria being
employed for forming metal (particularly, zinc) gallate spinel
structures are mesophilic (20-45.degree. C.) or psychrophilic (less
than 20.degree. C.).
[0045] The culture medium, i.e., biological medium 5b, for
sustaining the fermentative or thermophilic bacteria, can be an
aqueous-based medium. The culture medium may also facilitate growth
of the bacteria. In one embodiment, an anaerobic culture vessel is
provided that contains the aqueous-based medium in which the
bacteria are grown anaerobically. Additives such as electron
donors, vitamins, trace elements, and other nutrients are included
in the culture medium. An electron donor is any compound or
material capable of being oxidatively consumed by the bacteria such
that donatable electrons are provided to the bacteria by the
consumption process.
[0046] In one embodiment, the electron donor, e.g., nutrient 5c,
includes one or more carboxylate-containing compounds that can be
oxidatively consumed by the fermentative or thermophilic bacteria.
Some examples of suitable carboxylate-containing compounds include
formate, acetate, propionate, butyrate, oxalate, malonate,
succinate, fumarate, glutarate, lactate, pyruvate, glyoxylate,
glycolate, and citrate.
[0047] In another embodiment, the electron donor includes one or
more sugars (i.e., saccharides, disaccharides, oligosaccharides, or
polysaccharides) that can be oxidatively consumed by the
fermentative or thermophilic bacteria. Some examples of suitable
sugars include glucose, fructose, sucrose, galactose, maltose,
mannose, arabinose, xylose, lactose, and disaccharides therefrom,
oligosaccharides therefrom, or polysaccharides therefrom.
[0048] In another embodiment, the electron donor includes one or
more inorganic species that can be oxidatively consumed by the
fermentative or thermophilic bacteria. The inorganic species can
be, for example, an oxidizable gas, such as hydrogen. Such gases
can be oxidized by hydrogen-consuming microbes, which have the
capacity to reduce one or more metals or non-metal compounds by the
produced electrons. It is noted that the above electron donors are
purely exemplary and not intended to limit the present disclosure
to any of the materials and concentrations described herein. In
some embodiments, and one or more classes or specific types of
electron donors are excluded from the process.
[0049] In one embodiment, the concentration of electron donor
within an aqueous-based medium that provides the culture medium for
the fermentative or thermophilic bacteria ranges from 1.0 mM to 20
mM. In another embodiment, the concentration of electron donor
within the an aqueous-based media that provides the culture medium
for the fermentative or thermophilic bacteria ranges from 0.4 mM to
1.0 mM. In yet another embodiment, the concentration of electron
donor within the an aqueous-based media that provides the culture
medium for the fermentative or thermophilic bacteria ranges from
0.5 mM to 1.5 mM. Example concentrations for the electron donor
within the aqueous-based media that provides the culture medium for
the fermentative or thermophilic bacteria include 0.4 mM, 0.5 mM,
0.6 mM, 1.0 mM, 1.5 mM, 4, mM, 6 mM and 20 mM. Any range resulting
from any two of the foregoing values is also contemplated
herein.
[0050] In one embodiment, the method of nucleating metal gallate
(and particularly, zinc gallate) spinel structures with
fermentative or thermophilic bacteria includes providing at least
one divalent metal-containing (or zinc-containing) salt (and
optionally, one or more monovalent or trivalent metal-containing
salts) at step 10 of the process sequence depicted in FIG. 1A. The
divalent metal-containing salt may be any ionic compound that
dissociates to provide a divalent metal cation, such as Zn.sup.2+,
Cu.sup.2+, or Cd.sup.2+. In some embodiments, the divalent
metal-containing salt may be a bromide, hydrate, phosphate,
stearate, fluoride, acrylate, or combination thereof, of a divalent
metal. Some examples of zinc-containing salts include zinc chloride
(ZnCl.sub.2), zinc bromide (ZnBr.sub.2), zinc nitrate hydrate
(Zn(NO.sub.3).sub.2.xH.sub.2O), zinc sulfate hydrate
(ZnSO.sub.4.xH.sub.2O), zinc phosphate (Zn.sub.3(PO.sub.4).sub.2),
zinc acetate hydrate ((CH.sub.3CO.sub.2).sub.2Zn).xH.sub.2O), zinc
stearate ([CH.sub.3(CH.sub.2).sub.16COO].sub.2Zn), zinc fluoride
(ZnF.sub.2), zinc iodide (ZnI.sub.2), zinc methoxide
(C.sub.2H.sub.6O.sub.2Zn), zinc acrylate
((H.sub.2C.dbd.CHCO.sub.2).sub.2Zn), and combinations thereof. Some
examples of copper-containing salts include cupric chloride
(CuCl.sub.2), cuprous chloride (CuCl), cupric bromide (CuBr.sub.2),
cuprous bromide (CuBr), cupric nitrate
(Cu(NO.sub.3).sub.2.xH.sub.2O), and cupric sulfate
(CuSO.sub.4.xH.sub.2O), where x may be 0 or an integer of at least
one. Some examples of cadmium-containing salts include cadmium
chloride (CdCl.sub.2), cadmium bromide (CdBr.sub.2), cadmium
nitrate (Cd(NO.sub.3).sub.2.xH.sub.2O), and cadmium sulfate
(CuSO.sub.4.xH.sub.2O), where x may be 0 or an integer of at least
one. Some examples of monovalent metal-containing salts include
compounds of the formula M.sub.vX.sup.-m.sub.w, wherein M is a
monovalent metal (e.g., Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+,
Cu.sup.+, Ag.sup.+, or Tl.sup.+), X is a negatively charged group
(with oxidation state -m), such as, for example, a halide (e.g.,
F.sup.-, Cl.sup.-, Br.sup.-, or I.sup.-), hydroxide, alkoxide,
carbonate, sulfate, sulfite, nitrate, nitrite, phosphate, acrylate,
or stearate group, and v and w subscripts are integers, such that
v=m.times.w. Some examples of trivalent metal-containing salts
include compounds of the formula M'.sub.vX.sup.-m.sub.w, wherein M
is a trivalent metal, such as any of the trivalent metal species
provided above, X is a negatively charged group (with oxidation
state -m), such as any of the negatively charged groups provided
above, and v and w subscripts are integers, such that
3v=m.times.w.
[0051] It is noted that the above description of monovalent,
divalent, and trivalent metal-containing salts is provided for
illustrative purposes only, and is not intended to limit the
present disclosure, as other such metal-containing salts are
suitable for use with the methods disclosed herein. For example,
any metal-containing salt is suitable for use with the methods and
compositions of the present disclosure, so long as the
metal-containing salt is capable of forming a metal gallate spinel
structure that is nucleated with fermentative or thermophilic
bacteria without reduction of the metal.
[0052] In one embodiment, the method of nucleating metal gallate
spinel structures with fermentative or thermophilic bacteria
includes providing at least one gallium-containing salt at step 15
of the process sequence depicted in FIG. 1A. The gallium-containing
salt may be any ionic compound that dissociates to provide a
gallium cation, e.g., Ga.sup.3+. In some embodiments, the
gallium-containing salt may be a chloride, hydroxide, bromide,
fluoride, iodide, or combination thereof, of gallium. In some
examples, the gallium-containing salt may include at least one
gallium-containing salt selected from the group consisting of
gallium chloride (e.g., GaCl.sub.3 or GaCl.sub.2), gallium nitrate
(GaNO.sub.3.xH.sub.2O), gallium fluoride (GaF.sub.3), gallium
iodide (GaI.sub.3), gallium bromide (GaBr.sub.3), gallium sulfate
(GaSO.sub.4.xH.sub.2O), and combinations thereof. It is noted that
the above description of gallium-containing salts is provided for
illustrative purposes only, and is not intended to limit the
present disclosure, as other gallium-containing salts are suitable
for use with the methods disclosed herein. For example, any
gallium-containing salt is suitable for use with the methods and
compositions of the present disclosure, so long as the
gallium-containing salt is capable of forming a divalent metal
gallate spinel structure that is nucleated with fermentative or
thermophilic bacteria without reduction of the gallium.
[0053] The divalent metal-containing salt, gallium-containing salt,
electron donor, and the fermentative or thermophilic bacteria are
then combined to nucleate a divalent metal gallate spinel without
reduction of at least a divalent metal ion from the
metal-containing salt as step 20 of the process sequence that is
depicted in FIG. 1A. In some embodiments, the divalent
metal-containing salt, the gallium-containing salt and the
fermentative or thermophilic bacteria, including the culture media
(e.g., the electron donors, vitamins, trace elements, and other
nutrients included in the culture medium), are mixed in a suitable
container and subjected to conditions (e.g., temperature, pH, and
reaction time) suitable for producing a metal gallate spinel
structure from the reaction components. In one embodiment, the
container for holding the reaction components is simple by
containing no more than container walls, a bottom, and a lid. In
another embodiment, the container is more complex by including
additional features, such as inlet and outlet elements for gases,
liquids, or solids, one or more heating elements, nanoparticle
separation features (e.g., traps or magnets), one or more agitating
elements, fluid recirculating elements, electronic controls for
controlling one or more of these or other conditions, and so
on.
[0054] FIG. 2 is one embodiment of a simplified diagram of a batch
type reactor 30 suitable for carrying out the inventive process
shown in FIG. 1A. The reactor includes a container 31 constructed
of glass or other inert material. A culture medium 32 is introduced
in the container 31. The culture medium 32 may contain an aqueous
solution of the fermentative or thermophilic bacteria, electron
donors, nutrients, vitamins, trace elements, vitamins, and other
compounds as described in the foregoing examples. The container 31
is sealed to prevent the entry of air into the headspace gas region
33 thereby maintaining anaerobic conditions within the culture, as
well as permitting the inventive process to be carried out at
pressures greater or less than ambient if desired. A gas conduit 34
is included to allow the introduction of selected gases into the
container 31 and to allow gases to exit the container 31. An
electron donor is introduced into the culture either as a gas (such
as hydrogen along with a relatively inert diluent or carrier gas
such as N.sub.2, Ar, He, CO.sub.2) through the gas conduit 34, or
dissolved directly into the culture medium 34 in the case of simple
organics, such as glucose, lactate, and pyruvate. The
zinc-containing salt and the gallium-containing salt may be
introduced to the culture medium 32 including the fermentative or
thermophilic bacteria.
[0055] In one embodiment, the divalent metal-containing salt is
present in the aqueous solution with the fermentative or
thermophilic bacteria in a concentration ranging from 0.01 mM to 10
mM. In another embodiment, the divalent metal-containing salt is
present in the aqueous solution with the fermentative or
thermophilic bacteria in a concentration ranging from 1.5 mM to 3
mM. In yet another embodiment, the divalent metal-containing salt
is present in the aqueous solution with the fermentative or
thermophilic bacteria in a concentration ranging from 1.8 mM to 2.1
mM. Some exemplary concentrations for the divalent metal-containing
salt present in the aqueous solution may include 1.88 mM, 1.92 mM,
1.96 mM, 1.98 mM and 2 mM.
[0056] In one embodiment, the gallium-containing salt is present in
the aqueous solution with the fermentative or thermophilic bacteria
in a concentration ranging from 0.02 mM to 20 mM. In another
embodiment, the gallium-containing salt is present in the aqueous
solution with the fermentative or thermophilic bacteria in a
concentration ranging from 3 mM to 5 mM. In yet another embodiment,
the gallium-containing salt is present in the aqueous solution with
the fermentative or thermophilic bacteria in a concentration
ranging from 3.75 mM to 4 mM. Some exemplary concentrations for the
gallium-containing salt present in the aqueous solution may include
3.6 mM, 3.76 mM, 3.8 mM, 3.84 mM, 3.92 mM, 3.96 mM and 4 mM.
[0057] The fermentative or thermophilic bacteria, the
metal-containing salt, and the gallium-containing salt, as well as
other additives employed in the formation of the divalent metal
gallate structure, may be combined in any suitable manner in the
batch reactor 30. For example, each of the above-referenced
reaction components or a combination thereof may be prepared before
the components are combined, or alternatively, obtained in a
pre-packaged form before the components are combined. When
components or combinations thereof are provided in package form,
the packaged forms may be designed to be used in their entireties,
or alternatively, designed such that a portion of each is used
(e.g., as aliquots of a concentrate). In some embodiments, the
order of addition of components has essentially no bearing on the
final compositional and physical characteristics of the produced
divalent metal gallate spinel structures. In other embodiments, the
compositional and/or physical characteristics of the resulting
divalent metal gallate spinel structures are affected in some way
by the order in which components are combined.
[0058] Referring to FIG. 2, a heating element 35 existing inside
and/or outside of container 31 is provided proximate the container
31 to maintain the culture medium 32 at a desired temperature for
growth of the fermentative or thermophilic bacteria. When
fermentative or thermophilic bacteria are used in aqueous solution
with the metal-containing salt and gallium-containing salt, the
temperature at which the reaction is conducted can be at least, for
example, 40.degree. C., 45.degree. C., 50.degree. C., 55.degree.
C., 60.degree. C., 65.degree. C., 70.degree. C., 75.degree. C.,
80.degree. C., 85.degree. C., or 90.degree. C., depending on the
type of microbes being used. Any range resulting from any two of
the foregoing values is also contemplated herein. When mesophilic
bacteria are used, the temperature can be at least 15.degree. C.,
20.degree. C., 25.degree. C., or 30.degree. C., and up to any of
the temperatures given above for the fermentative or thermophilic
bacteria. When psychrophilic bacteria are used, the temperature at
which the reaction is conducted can be less than, for example,
40.degree. C., or at or less than 35.degree. C., 30.degree. C.,
25.degree. C., 20.degree. C., 15.degree. C., 10.degree. C.,
5.degree. C., 0.degree. C., or -5.degree. C., or any range
resulting from any two of the foregoing values. In one example,
when employing Thermoanaerobacter sp. strain TOR-39, the
temperature is preferably maintained between 45.degree. C. and
75.degree. C.
[0059] In some embodiments, the fermentative or thermophilic
bacteria function as nucleating agents or templates in the
crystallization of the spinel structure for the metal-containing
salt, the gallium-containing salt, and the water component of the
aqueous solution. Without being bound by any theory, it is believed
that the fermentative or thermophilic bacteria are organizing the
salts, i.e., metal-containing salt and gallium-containing salt, and
the water into the A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2 crystal
spinel structure of the divalent metal gallate spinel. As indicated
above, the nucleation of the divalent metal gallate structure from
the divalent metal-containing salt and the gallium-containing salt
in the aqueous solution with the fermentative or thermophilic
bacteria is not a reduction reaction.
[0060] To precipitate the divalent metal gallate spinel structure
from the aqueous solution with the fermentative or thermophilic
bacteria, the pH of the aqueous solution containing the
metal-containing salt and the gallium-containing salt is adjusted
to range from 5.0 to 9.0 when residing in container 31. In another
embodiment, to precipitate the divalent metal gallate spinel
structure from the aqueous solution with the fermentative or
thermophilic bacteria, the pH of the aqueous solution containing
the divalent metal-containing salt and the gallium-containing salt
is adjusted to range from 5.5 to 8.5. In yet another embodiment, to
precipitate the divalent metal gallate spinel structure from the
aqueous solution with the fermentative or thermophilic bacteria,
the pH of the aqueous solution containing the divalent
metal-containing salt and the gallium-containing salt is adjusted
to range from 6.0 to 8.0. In an even further embodiment, to
precipitate the divalent metal gallate spinel structure from the
aqueous solution with the fermentative or thermophilic bacteria,
the pH of the aqueous solution containing the divalent
metal-containing salt and the gallium-containing salt is adjusted
to range from 6.5 to 8.0. In some examples, the divalent metal
gallate spinel structures may be precipitated from an aqueous
solution of divalent metal-containing salt and gallium-containing
salt in the presence of fermentative or thermophilic bacteria, in
which the pH of the aqueous solution is 6.41, 6.42, 6.43, 7.57,
7.60 or 7.61. Moreover, the pH of the aqueous solution may be
adjusted with one or more pH buffers. Some examples of buffers
include sodium hydroxide, potassium hydroxide, hydrochloric acid,
N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) (HEPES),
N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt
(HEPES sodium salt), 3-(N-morpholino)propanesulfonic acid
(MOPS),3-(N-morpholino)propanesulfonic acid sodium salt (MOPS
sodium salt), and other buffers commonly used in biological
research as provided in Good et al., 1966, Biochemistry
5:467-477.
[0061] To precipitate the divalent metal gallate spinel structure
from the aqueous solution with the fermentative or thermophilic
bacteria, the reduction potential (E.sub.h) of the aqueous solution
containing the divalent metal-containing salt and the
gallium-containing salt is preferably adjusted to be within the
range of 100 mV to -350 mV. In one embodiment, to precipitate the
divalent metal gallate spinel structure from the aqueous solution
with the fermentative or thermophilic bacteria, the reduction
potential (E.sub.h) of the aqueous solution containing the divalent
metal-containing salt and the gallium-containing salt is adjusted
to be within the range of 50 mV to -250 mV. In another embodiment,
to precipitate the divalent metal gallate spinel structure from the
aqueous solution with the fermentative or thermophilic bacteria,
the reduction potential (E.sub.h) of the aqueous solution
containing the divalent metal-containing salt and the
gallium-containing salt is adjusted to be within the range of 0 mV
to -150 mV. In yet another embodiment, to precipitate the divalent
metal gallate spinel structure from the aqueous solution with the
fermentative or thermophilic bacteria, the reduction potential
(E.sub.h) of the aqueous solution containing the divalent
metal-containing salt and the gallium-containing salt is adjusted
to be within the range of -100 mV to -145 mV. In some examples, the
divalent metal gallate spinel structures may be precipitated from
an aqueous solution of divalent metal-containing salt and
gallium-containing salt in the presence of fermentative or
thermophilic bacteria, in which the reduction potential (E.sub.h)
of the aqueous solution is -110 mV, -111 mV, -119 mV, -137 mV, -138
mV or -142 mV. The reduction potential (E.sub.h) of the aqueous
solution may be adjusted by adjusting the electron donors,
microbial activity, reducing agents (e.g. cysteine), or addition of
external current (e.g. direct current) in the aqueous solution.
[0062] A divalent metal gallate spinel structure forms in the
container 32 as the bacteria nucleates the spinel structure from
the divalent metal-containing salt, the gallium-containing salt,
and the water component of the aqueous solution. As the crystal
size of the spinel structures increases, the divalent metal gallate
spinel structures precipitate from solution. In some embodiments,
the divalent metal gallate spinel is a zinc gallate spinel
structure of the composition ZnGa.sub.2O.sub.4. In other
embodiments, the divalent metal gallate spinel is a copper gallate
spinel structure of the composition CuGa.sub.2O.sub.4. In other
embodiments, the divalent metal gallate spinel is a cadmium gallate
spinel structure of the composition CdGa.sub.2O.sub.4. The relative
molar ratio of the divalent metal may diverge from 1, and the
relative molar ratio of Ga may diverge from 2 when 0 is set to
4.
[0063] The divalent metal gallate spinel objects that precipitate
from the aqueous solution containing the fermentative or
thermophilic bacteria, the divalent metal-containing salt, and the
gallium-containing salt preferably have a largest dimensional axis
of 1 micron or less. The spinel structures disclosed herein are
generally nano-objects (e.g., nanoparticles), which typically have
at least one of their dimensional axes up to 500 nm or less. In
different embodiments, the divalent metal gallate spinel structure
can have a largest axis ranging 1 nm to 500 nm. For example, the
divalent metal gallate spinel structure can have a largest axis of
2 nm, 3 nm, 4 nm, 5 nm, 10 nm, 12 nm, 15 nm, 20 nm, 25 nm, 30 nm,
40 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 400 nm, or
500 nm, or any range therebetween (e.g., 1-10 nm, 2-10 nm, 1-20 nm,
2-20 nm, 3-20 nm, 1-500 nm, 5-500 nm, 1-150 nm, or 5-150 nm). In
one embodiment, the divalent metal gallate objects are
nanoparticles that are fairly disperse in size (e.g., having a size
variation of 20%, 30%, 40%, 50%, or greater from a median or mean
size). In another embodiment, the nanoparticles are fairly
monodisperse in size (e.g., having a size variation of or less than
50%, 40%, 30%, 20%, 10%, 5%, 2%, or 1% from a median or mean size).
When the divalent metal gallate spinel structure has a spherical
geometry, the largest axis would be the diameter of the divalent
metal gallate spinel structure.
[0064] Referring to FIG. 2, when a sufficient quantity of divalent
metal gallate spinel 36 has been precipitated and allowed to settle
to the bottom of the container 31, the culture medium 32 is
decanted or siphoned and the precipitated divalent metal gallate
spinel 36 is collected and washed. The reaction (incubation) time
is the period of time that the combined reaction components are
subjected to reaction conditions necessary for producing divalent
metal gallate spinel 36. Shorter reaction times (e.g., 1-60
minutes) may be used at elevated temperature conditions, whereas
longer reaction times (e.g., 1-7 days, or 1-3 weeks) may be used at
lower temperatures to obtain a similar yield of product. Typically,
shorter reaction times produce smaller particles than particles
produced using longer reaction times under the same conditions. The
incubation may be, for example, between 3 and 30 days, depending on
the amount and size of the crystalline nanoparticle product
desired.
[0065] The above-described process may also be performed in a
continuous arrangement as shown schematically by the bioreactor 40
shown in FIG. 3. The bioreactor 40 operates in a similar manner as
the bioreactor 30 of FIG. 2. The bioreactor 40 includes a fluid
recirculator 41 that allows the culture medium 32 to pass through
an external trap 42 from which the precipitated divalent metal
gallate spinel 36 can be removed. The trap 42 may separate the
precipitated divalent metal gallate spinel 36 from the circulating
culture medium by settling, due to the greater density of the
divalent metal gallate spinel 36. In some cases, the collection
process of the precipitated divalent metal gallate spinel 36 can be
assisted by using a continuous centrifuge 43. Continuous collection
of product from the circulating fluid may also be used as a means
of controlling particle size, because the particles tend to grow
larger the longer they remain in the culture. An additional fluid
valve 44 may be provided through which additional culture medium or
nutrients 34 may be added from an external reservoir 45 while
maintaining the anaerobic conditions within the container 32.
[0066] The divalent metal gallate spinel structures foamed using
the process flow depicted in FIG. 1A, and the apparatuses depicted
in FIGS. 2 and 3, may be an undoped or pure divalent metal gallate
spinel structure. By "pure" is meant that the spinel structure is
completely free of dopants, such as manganese (Mn), cobalt (Co),
chromium (Cr), europium (Eu), dysprosium (Dy) and combinations
thereof. Alternatively, the spinel structure may be doped by one or
more metals, such as any of the foregoing exemplary metals. The
only elements present in a pure zinc gallate spinel structure are
those within the formulation A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2-,
in which cations A and B occupy some or all of the tetrahedral and
octahedral sites in the lattice, wherein 98% of the A site is
occupied by a divalent metal cation and 98% of the B site is
occupied by a gallium cation. In some embodiments, impuritites may
be present so long as their concentration does not change the
emission for the wavelength of the divalent metal gallate spinel
structures. For example, the impurities may be elements that are
not within the desired stoichiometry for the A site and the B site
of the formulation A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2, which may
result from the processing. Some examples of impurity include, but
are not limited to phosphorus, silicon, carbon and aluminum. In one
example, a pure divalent metal gallate spinel structure has the
formulation A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2-, in which cations
A and B occupy some or all of the tetrahedral and octahedral sites
in the lattice, wherein about 100% of the A site is occupied by a
divalent metal cation and about 100% of the B site is occupied by a
gallium cation.
[0067] In some embodiments, the undoped divalent metal (and
particularly, zinc) gallate spinel structure may function as a blue
and/or violet light emitting phosphor. In one embodiment, the
wavelength of the undoped divalent metal gallate spinel may exhibit
a peak ranging from 400 nm to 495 nm. In another embodiment, the
wavelength of the undoped divalent metal gallate spinel ranges from
425 nm to 435 nm. In some examples, the peak wavelength of light
emission of the undoped divalent metal gallate spinel is 415 nm,
420 nm, 425 nm, 430 nm, 435 nm, 440 nm, 445 nm, 450 nm, 455 nm, 460
nm, 465 nm, 470 nm, 475 nm, 480 nm, 485 nm, and 490 nm, or may be
within a range bounded by any of these values.
[0068] FIG. 4 is a process diagram illustrating a method of forming
doped divalent metal gallate spinel structures with fermentative or
thermophilic bacteria. The process flow depicted in FIG. 4 is
similar to the process flow that is described above with reference
to FIG. 1A with the exception that a dopant source is combined with
the divalent metal-containing salt, the gallium-containing salt,
and the fermentative or thermophilic bacteria. The fermentative or
thermophilic bacteria, divalent metal-containing salt and
gallium-containing salt that are described above in the process
sequence depicted in FIG. 1A are suitable for the fermentative or
thermophilic bacteria, divalent metal-containing salt and
gallium-containing salt of the method of forming a doped divalent
metal gallate spinel structure as illustrated in FIG. 4. Therefore,
the description of steps 5, 10 and 15 of the method of nucleating a
divalent metal gallate spinel structure with fermentative or
thermophilic bacteria that is described with reference to FIG. 1A,
is suitable for the description of steps 50, 55 and 60 of the
method of forming doped divalent metal gallate spinel structures
with fermentative or thermophilic bacteria that is illustrated in
FIG. 4.
[0069] Referring to step 65 of FIG. 4, in one embodiment, a dopant
source is provided for tuning a wavelength of emission from the
divalent metal gallium spinel structure, wherein the dopant source
may be selected from the group consisting of manganese (Mn),
chromium (Cr), europium (Eu), dysprosium (Dy), cobalt (Co), and
combinations thereof. The dopant may be any element of the Periodic
Table. In some embodiments, one or more dopants are excluded.
Typically, the dopants are substitution type dopants. A
substitution type dopant replaces a portion of the elements that
occupy the A and B lattice sites for the divalent metal gallate
spinel structure, which has the spinel formulation
A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2-. For example, in one
embodiment, in which the dopant is manganese (Mn) having an
oxidation state of 2+, the manganese ion (Mn.sup.2+) may be
substituted for the divalent metal ion (e.g., Zn.sup.2+) that
occupies the A lattice site of the spinel having the formulation
A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2-. In the embodiments in which
the dopant is manganese (Mn) having the oxidation state 3+, the
manganese ion (Mn.sup.3+) may be substituted for the gallium ion
(Ga.sup.3+) that occupies the B lattice site of the spinel having
the formulation A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2-. The occupancy
to either tetrahedral or octahedral site may vary according to
doping elements, concentration, valences, ionic radii, therefore
divalent dopants may occupy octahedral sites in some extent or
trivalent dopants may occupy tetrahedral sites in some extent.
[0070] In one embodiment, to dope the divalent metal gallate spinel
structure with a manganese (Mn) dopant, i.e., Mn.sup.2+ or
Mn.sup.3+, the divalent metal gallate spinel structure is doped
with at least one of manganese chloride hydrate
(MnCl.sub.2.xH.sub.2O), manganese nitrate hydrate
(Mn(NO.sub.3).sub.2.xH.sub.2O), manganese sulfate hydrate
(MnSO.sub.4.xH.sub.2O), manganese iodide (MnI.sub.2), manganese
bromide (MnBr.sub.2), manganese fluoride (MnF.sub.3), manganese
acetate hydrate (Mn(CH.sub.3COO).sub.2.xH.sub.2O), and manganese
carbonate (MnCO.sub.3), which is mixed with the aqueous solution
including the divalent metal-containing salt, the
gallium-containing salt and the fermentative or thermophilic
bacteria. The concentration of manganese (Mn) dopant, i.e.,
Mn.sup.2+ or Mn.sup.3+, may range from 0.01% to 10% of divalent
metal, gallium, or their combined concentration. In another
embodiment, the concentration of manganese (Mn) dopant, i.e.,
Mn.sup.2+ or Mn.sup.3+, may range from 0.02% to 8%. In yet another
embodiment, the concentration of manganese (Mn) dopant, i.e.,
Mn.sup.2+ or Mn.sup.3+, ranges from 0.04% to 6%. In some examples,
the concentration of manganese (Mn) dopant, i.e., Mn.sup.2+ or
Mn.sup.3+, may be 0.01%, 2%, 4%, 6%, and 8%. Any range of manganese
(Mn) concentration between the aforementioned examples is also
contemplated. The doping of the divalent metal gallate spinel with
manganese (Mn) dopant, i.e., Mn.sup.2+ or Mn.sup.3, when treated
with the subsequently described heat treatment provides a
wavelength of light emission that ranges from 495 nm to 570 nm.
[0071] In one embodiment, to dope the divalent metal gallate spinel
structure with a chromium dopant, e.g., Cr.sup.3+, the divalent
metal gallate spinel structure is doped with at least one of
chromium chloride hydrate (CrCl.sub.3.xH.sub.2O), chromium nitrate
hydrate (Cr(NO.sub.3).sub.3.xH.sub.2O), chromium acetate hydroxide
((CH.sub.3CO.sub.2).sub.7Cr.sub.3(OH).sub.2), chromium sulfate
hydrate (Cr.sub.2(SO.sub.4).sub.3.xH.sub.2O), chromium fluoride
hydrate (GaF.sub.3.xH.sub.2O), chromium iodide hydrate
(GaI.sub.3.xH.sub.2O), chromium bromide hydrate
(GaBr.sub.3.xH.sub.2O), chromium phosphate hydrate
(Cr(PO.sub.4).xH.sub.2O) or a combination of the above chromium
containing substances. The chromium dopant, i.e., Cr.sup.3+, is a
substitutional dopant for gallium, in the divalent metal gallate
spinel structure. More specifically, the chromium dopant, i.e.,
Cr.sup.3+, occupies the B lattice site of the spinel having the
formulation A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2-. The dopant source
for the chromium dopant is mixed with the aqueous solution
including the divalent metal-containing salt, the
gallium-containing salt, and the fermentative or thermophilic
bacteria. The concentration of chromium (Cr) dopant, i.e.,
Cr.sup.3+, may range from 0.01% to 6% of divalent metal, gallium,
or their combined concentration. In another embodiment, the
concentration of chromium (Cr) dopant, i.e., Cr.sup.3+, may range
from 0.04% to 6%. In yet another embodiment, the concentration of
chromium (Cr) dopant, i.e., Cr.sup.3+, ranges from 0.08% to 4%. In
some examples, the concentration of chromium (Cr) dopant, i.e.,
Cr.sup.3+, may be 0.01%, 0.5%, 2%, 4% or 6%. Any range of chromium
(Cr) concentration between the aforementioned examples is also
contemplated. The doping of the zinc gallate spinel with chromium,
e.g., Cr.sup.3+, when treated with the subsequently described heat
treatment provides a wavelength of light emission that ranges from
570 nm to 750 nm.
[0072] In one embodiment, to dope the divalent metal gallate spinel
structure with a europium dopant, e.g., Eu.sup.3+, the zinc gallate
spinel structure is doped with at least one of europium chloride
hydrate (EuCl.sub.3.xH.sub.2O), europium fluoride hydrate
(EuF.sub.3.xH.sub.2O), europium nitrate hydrate
(Eu(NO.sub.3).sub.3.xH.sub.2O), europium acetate hydroxide
((CH.sub.3CO.sub.2).sub.7Eu.sub.3(OH).sub.2), europium bromide
hydrate (EuBr.sub.3.xH.sub.2O) and europium sulfate hydrate
(Eu.sub.2(SO.sub.4).sub.3.xH.sub.2O). The europium dopant, i.e.,
Eu.sup.3+, is a substitutional dopant for gallium, in the divalent
metal gallate spinel structure. More specifically, the europium
dopant, i.e., Eu.sup.3+, occupies the B lattice site of the spinel
having the formulation A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2-. The
dopant source for the europium dopant is mixed with the aqueous
solution including the divalent metal-containing salt, the
gallium-containing salt, and the fermentative or thermophilic
bacteria. The concentration of europium (Eu) dopant, i.e.,
Eu.sup.3+, may range from 0.01% to 20% of divalent metal, gallium,
or their combined concentration. In another embodiment, the
concentration of europium (Eu) dopant, i.e., Eu.sup.3+, may range
from 0.01% 20% of divalent metal, gallium, or their combined
concentration. In yet another embodiment, the concentration of
europium (Eu) dopant, i.e., Eu.sup.3+, ranges from 0.04% to 15%. In
some examples, the concentration of europium (Eu) dopant, i.e.,
Eu.sup.3+, may be 0.01%, 0.5%, 2%, 5%, 10% and 20%. Any range of
europium (Eu) concentration between the aforementioned examples is
also contemplated. The doping of the zinc gallate spinel with
europium (Eu) dopant, e.g. Eu.sup.3+, when treated with the
subsequently described heat treatment provides a wavelength of
light emission that ranges from 570 nm to 750 nm.
[0073] In one embodiment, to dope the divalent metal gallate spinel
structure with a dysprosium (Dy) dopant, e.g., Dy.sup.3+, the
divalent metal gallate spinel structure is doped with at least one
of dysprosium chloride hydrate (DyCl.sub.3.xH.sub.2O), dysprosium
fluoride hydrate (DyF.sub.3.xH.sub.2O), dysprosium nitrate hydrate
(Dy(NO.sub.3).sub.3.xH.sub.2O), dysprosium acetate hydroxide
((CH.sub.3CO.sub.2).sub.7Dy.sub.3(OH).sub.2), dysprosium bromide
hydrate (DyBr.sub.3.xH.sub.2O), dysprosium sulfate hydrate
(Dy.sub.2(SO.sub.4).sub.3.xH.sub.2O). The dysprosium dopant, i.e.,
Dy.sup.3+, is a substitutional dopant for gallium, in the divalent
metal gallate spinel structure. More specifically, the dysprosium
dopant, i.e., Dy.sup.3+, occupies the B lattice site of the spinel
having the formulation A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2-. The
dopant source for the dysprosium dopant is mixed with the aqueous
solution including the divalent metal-containing salt, the
gallium-containing salt, and the fermentative or thermophilic
bacteria. The concentration of dysprosium (Dy) dopant, i.e.,
Dy.sup.3+, may range from 0.01% to 10% of divalent metal, gallium,
or their combined concentration. In another embodiment, the
concentration of dysprosium (Dy) dopant, i.e., Dy.sup.3+, may range
from 0.02% to 8%. In yet another embodiment, the concentration of
dysprosium (Dy) dopant, i.e., Dy.sup.3+, ranges from 0.04% to 6%.
In some examples, the concentration of dysprosium (Dy) dopant,
i.e., Dy.sup.3+, may be 0.01%, 0.5%, 2%, 4%, and 7%. Any range of
dysprosium (Dy) concentration between the aforementioned examples
is also contemplated. The doping of the zinc gallate spinel with
dysprosium (Dy) dopant, e.g. Dy.sup.3+, when treated with the
subsequently described heat treatment provides a wavelength of
light emission that ranges from 450 nm to 510 nm. In another
embodiment, the doping of the zinc gallate spinel with dysprosium
(Dy) dopant, e.g. Dy.sup.3+, when treated with the subsequently
described heat treatment provides a wavelength of light emission
that ranges from 560 nm to 610 nm. In an even further embodiment,
the doping of the zinc gallate spinel with dysprosium (Dy) dopant,
e.g. Dy.sup.3+, when treated with the subsequently described heat
treatment provides a wavelength of light emission that ranges from
755 nm to 810 nm. In some embodiments, zinc gallate spinel
structure with a dysprosium (Dy) dopant can produce white light by
itself. In some examples, zinc gallate spinel structures doped with
a dysprosium (Dy) has 4 groups of characteristic lines in the
dopant emission spectra at the same time, e.g., lines in blue
region (450 nm to 510 nm), lines in the yellow region (560 nm-610
nm), and two groups of line spectra in the red region 660 nm to 720
nm and 755 nm to 800 nm).
[0074] In one embodiment, to dope the divalent metal gallate spinel
structure with a cobalt dopant, e.g., Co.sup.2+, the divalent metal
gallate spinel structure is doped with at least one of cobalt
chloride hydrate (CoCl.sub.2.xH.sub.2O), cobalt nitrate hydrate
(Co(NO.sub.3).sub.2.xH.sub.2O), cobalt sulfate hydrate
(CoSO.sub.4.xH.sub.2O), cobalt iodide (CoI.sub.2), cobalt bromide
(CoBr.sub.2), cobalt fluoride (CoF.sub.3), cobalt acetate hydrate
(Co(CH.sub.3COO).sub.2.xH.sub.2O), and cobalt carbonate
(CoCO.sub.3), which is mixed with the aqueous solution including
the divalent metal-containing salt, the gallium-containing salt,
and the fermentative or thermophilic bacteria. The cobalt dopant,
i.e., Co.sup.2+, is a substitutional dopant for the divalent metal
in the divalent metal gallate spinel structure. More specifically,
the cobalt dopant, i.e., Co.sup.2+, occupies the A lattice site of
the spinel having the formulation
A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2-. The dopant source for the
cobalt dopant is mixed with the aqueous solution including the
divalent metal-containing salt, the gallium-containing salt, and
the fermentative or thermophilic bacteria. The concentration of
cobalt (Co) dopant, i.e., Co.sup.2+, may range from 0.01% to 10% of
divalent metal, gallium, or their combined concentration. In
another embodiment, the concentration of cobalt (Co) dopant, i.e.,
Co.sup.2+, may range from 0.02% to 8%. In yet another embodiment,
the concentration of cobalt (Co) dopant, i.e., Co.sup.2+, ranges
from 0.04% to 6%. In some examples, the concentration of cobalt
(Co) dopant, i.e., Co.sup.2+, may be 0.02%, 0.5%, 2%, 4%, and 10%.
Any range of cobalt (Co) concentration between the aforementioned
examples is also contemplated. The doping of the zinc gallate
spinel with cobalt (Co) dopant, e.g. Co.sup.2+, when treated with
the subsequently described heat treatment provides a wavelength of
light emission of blue and visible and near infrared emission that
ranges from 400 nm to 495 nm with the maximum peak of 470 nm using
the excitation at 254 nm.
[0075] Referring to step 70 of FIG. 4, in one embodiment, the
divalent metal-containing salt, the gallium-containing salt, the
doping source, e.g., at least one of manganese (Mn), chromium (Cr),
europium (Eu), dysprosium (Dy), and cobalt (Co), and the bacteria
are combined to nucleate a doped divalent metal gallate spinel
structure. Typically, the nucleation of the doped divalent metal
gallate spinel structure does not include a reduction reaction.
Step 70 of combining the reactants for the process flow that is
described with reference to FIG. 4 is similar to step 20 of
combining the reactants for the process flow that is described with
reference to FIG. 1A with the exception that the process flow
depicted in FIG. 4 further includes a dopant source for the
divalent metal gallate spinel structure. Therefore, the description
of step 20 in FIG. 1A for reacting the divalent metal-containing
salt, the gallium-containing salt, and the fermentative or
thermophilic bacteria to nucleate a divalent metal gallate spinel
without a reduction reaction is suitable for the description of
reacting the divalent metal-containing salt, the gallium-containing
salt, the dopant source, and the fermentative or thermophilic
bacteria in step 70 of the process flow for forming a doped
divalent metal gallate spinel structure that is depicted in FIG. 4.
Further, the above described batch reactor that is depicted in FIG.
2, and the continuous reactor that is described with reference to
FIG. 3, may each be employed at step 70 for reacting the divalent
metal-containing salt, the gallium-containing salt, the dopant
source, and the fermentative or thermophilic bacteria in step 70 of
the process flow for forming a doped divalent metal gallate spinel
structure that is illustrated in FIG. 4.
[0076] Referring to step 75 of FIG. 4, in one embodiment, the doped
divalent metal gallate spinel structures are typically annealed to
effectuate a wavelength shift from the dopant that has been
introduced to the spinel structure. The annealing process can
provide phosphors having emissions at green, yellow, orange or red
wavelengths. For example, the annealing process may effectuate a
wavelength shift (from pure divalent metal gallate to the doped
version) from approximately 450 nm to another peak position. In
some embodiments, the annealing process is applied to zinc gallate
structures that are doped with manganese (Mn), chromium (Cr),
europium (Eu), cobalt (Co), dysprosium (Dy) and combinations
thereof.
[0077] The annealing process may be provided by a thermal annealing
process, such as rapid thermal annealing, furnace annealing, laser
annealing, induction heating, or pulsed thermal processing, all of
which are well known in the art. The annealing atmosphere may be an
inert atmosphere, such as an argon (Ar) or nitrogen (N.sub.2)
atmosphere. In other embodiments, the annealing atmosphere may be
an oxygen-containing atmosphere, such as air. In one embodiment,
the doped divalent metal gallate spinel is annealed at a
temperature ranging from 750.degree. C. to 1050.degree. C. In
another embodiment, the doped divalent metal gallate spinel may be
annealed at a temperature ranging from 800.degree. C. to
1000.degree. C. In yet another embodiment, the doped divalent metal
gallate spinel may be annealed at a temperature ranging from
850.degree. C. to 950.degree. C. It is noted that the annealing can
be in a range bounded by any values between any of the endpoints of
the above ranges. In particular embodiments, the doped divalent
metal gallate spinel may be annealed at 810.degree. C., 825.degree.
C., 850.degree. C., 875.degree. C., 900.degree. C., 925.degree. C.,
950.degree. C., 975.degree. C. or within a range bounded by any two
of the foregoing values. The time for annealing may be as great as
two hours. In some embodiments, the time for annealing the doped
divalent metal gallate spinel structures may range from 15 minutes
to 45 minutes. In other embodiments, the time for annealing the
doped divalent metal gallate spinel structure may range from 20 to
40 minutes.
[0078] In particular embodiments, a pulse thermal process is used
in the annealing step. The pulse thermal method considered herein
can be any method that can subject particles to a pulse of intense
thermal (i.e., radiant) energy. Generally, the means by which the
radiant energy is produced does not substantially alter or degrade
the composition of the particles. In particular embodiments, the
radiant pulse is provided by an intense pulse of electromagnetic
radiation. To produce heat in a material, the electromagnetic
radiation is generally absorbed by the material and emitted as
thermal energy.
[0079] The annealing step can employ any temperature sufficient to
induce a wavelength shift. The temperature of the thermal pulse can
widely vary depending on the composition of the particles and the
type of particles desired (e.g., crystalline vs. amorphous). In
different embodiments, the thermal pulse employs a temperature of
precisely, about, at least, above, up to, or less than, for
example, 50, 75, 100, 120, 125, 150, 200, 250, 300, 350, 400, 450,
500, 600, 700, 800, 900, 1000, 1500, 1800, 2000, 2200, 2500, or
3000 degrees Celsius (.degree. C.), or a temperature within a range
bounded by any two of the foregoing exemplary temperature values,
wherein the term "about", used for the temperature, generally
indicates within .+-.5, .+-.4, .+-.3, .+-.2, or .+-.1.degree. C. of
the indicated temperature.
[0080] In the pulsed thermal process, one or more pulses are
applied to the particles. In one embodiment, a single pulse is
used. In another embodiment, more than one pulse (e.g., two, three,
or a multiplicity of pulses), separated by a time interval between
pulses, is used. The pulse duration of each pulse can widely vary
depending on such factors as the absorbing ability of the
particles, the particle size, the wavelength of light, the
temperature, and substrate (underlying layers) used. It is
understood that a longer pulse duration generally results in a
higher applied temperature.
[0081] Generally, the pulse duration is no more than 10, 5, or 1
second, and more typically, 100-500 milliseconds (ms). In different
embodiments, the pulse duration can be precisely, about, at least,
up to, or less than, for example, 1 second (i.e., 1000 ms), 500 ms,
400 ms, 300 ms, 200 ms, 100 ms, 50 ms, 20 ms, 10 ms, 5 ms, 1 ms
(i.e., 1000 microseconds, i.e., 1000 .mu.s), 900 .mu.s, 800 .mu.s,
700 .mu.s, 600 .mu.s, 500 .mu.s, 400 .mu.s, 300 .mu.s, 200 .mu.s,
100 .mu.s, 80 .mu.s, 50 .mu.s, 40 .mu.s, 30 .mu.s, 20 .mu.s, 10
.mu.s, 5 .mu.s, 2.5 .mu.s, 1 .mu.s, 0.5 .mu.s, 0.25 .mu.s, or 0.1
.mu.s, or a pulse duration within a range bounded by any of the
foregoing exemplary values. In different embodiments, the pulse
energy can be, precisely, about, at least, up to, or less than, for
example, 1, 2, 5, 10, 25, 50, 100, 200, 300, 400, 500, 600, 700,
800, 900, or 1000 J/cm.sup.2. As known in the art, a pulse power
(i.e., in W/cm.sup.2) can be derived by dividing the pulse energy
(i.e., in J/cm.sup.2) by the pulse duration (in seconds). In the
particular case of thermally treating particles on thermally
sensitive substrates (e.g., a plastic), the pulse thermal process
preferably employs a high energy density (e.g., >20 KW/cm.sup.2)
thermal pulse at low ambient temperature.
[0082] If multiple pulses are used, the pulse duration may be the
same or the pulse duration may vary across different pulses. For
example, in different embodiments, the pulse duration alternates,
or successively increases or decreases with time. When multiple
pulses are used, the time interval between pulses (i.e., the
periodicity) can also be appropriately selected. In different
embodiments, the time interval is maintained below the pulse
duration, maintained above the pulse duration, or increased or
decreased with time successively or in a pattern-wise manner. The
time interval can be, for example, precisely, about, at least, up
to, or less than, for example, any of the exemplary values provided
above for pulse duration, typically no more than about 1 or 2
seconds. The time interval may also be within a range bounded by
any of the aforesaid values and/or any of the values provided above
for pulse duration. The frequency of the pulses can be precisely,
about, at least, up to, or less than, for example, 1 min.sup.-1, 10
min.sup.-1, 20 min.sup.-1, 30 min.sup.-1, 40 min.sup.-1, 50
min.sup.-1, 1 sec.sup.-1 (1 Hz), 5 sec.sup.-1, 10 sec.sup.-1, 20
sec.sup.-1, 30 sec.sup.-1, 40 sec.sup.-1, 50 sec.sup.-1, 100
sec.sup.-1, 500 sec.sup.-1, 1000 sec.sup.-1, 5000 sec.sup.-1,
1.times.10.sup.4 sec.sup.-1, 5.times.10.sup.4 sec.sup.-1,
1.times.10.sup.5 sec.sup.-1, 5.times.10.sup.5 sec.sup.-1,
1.times.10.sup.6 sec.sup.-1, 5.times.10.sup.6 sec.sup.-1,
1.times.10.sup.7 sec.sup.-1, or 5.times.10.sup.7 sec.sup.-1, or a
frequency within a range bounded by any of the foregoing exemplary
values.
[0083] The pulse of electromagnetic radiation may be suitably
adjusted in several other ways. For example, the pulse of
electromagnetic radiation can be suitably adjusted, by means well
known in the art, in its amplitude, phase, and extent of
collimation. Collimation can be achieved by, for example, use of a
collimator, such as a collimation lens or parabolic or spherical
mirrors. Substantially collimated light corresponds to a laser
emission, which is also considered herein as the pulse of
electromagnetic radiation. The spectrum of the impinging radiation
may also be appropriately filtered to provide particular
wavelengths or a narrowed range of wavelengths.
[0084] The pulse of electromagnetic radiation can also be suitably
adjusted in its power (i.e. intensity). The intensity of the pulse
of electromagnetic radiation is generally at least 100 W/cm.sup.2.
In different embodiments, the pulse of electromagnetic radiation
can be precisely, about, at least, or above, for example, 100, 200,
500, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000,
1.times.10.sup.4, 1.5.times.10.sup.4, 2.times.10.sup.4,
2.5.times.10.sup.4, 3.times.10.sup.4, 3.5.times.10.sup.4,
4.times.10.sup.4, 4.5.times.10.sup.4, 5.times.10.sup.4,
5.5.times.10.sup.4, 6.times.10.sup.4, 6.5.times.10.sup.4,
7.times.10.sup.4, 7.5.times.10.sup.4, 8.times.10.sup.4,
9.times.10.sup.4, or 1.times.10.sup.5 W/cm.sup.2, or an intensity
within a range bounded by any of the foregoing exemplary
values.
[0085] In particular embodiments, the pulsed thermal method employs
a stabilized plasma arc high intensity radiation source, as
described, for example, in U.S. Pat. Nos. 4,027,185 and 4,700,102,
the contents of which are incorporated herein by reference in their
entirety. As described in said patents, the arc can be suitably
restricted by use of a vortexing liquid wall. Numerous
modifications and improvements of the plasma arc method are known.
For example, the instant invention incorporates by reference the
contents of U.S. Pat. No. 4,937,490, which describes a high
intensity radiation arc apparatus that includes liquid injecting
means, gas injecting means, and exhausting means in the arc chamber
in order to provide a liquid vortex motion and a gas vortex motion
to restrict the plasma arc. Further adjustments, modifications, and
optimizations of the processes and apparatuses taught in the
foregoing patents can be made to better conform with the aims and
goals of the instant invention, as described above. For example,
the processes and apparatuses taught in the foregoing patents can
be configured to emit a high intensity of electromagnetic
radiation, particularly of the infrared wavelengths. Other
modifications not contemplated in said foregoing patents may also
be necessary to make the arc plasma systems described therein
capable of operating within the parameters described herein, e.g.,
to provide any of the particular pulse durations, frequencies,
power, or wavelengths described above. In particular embodiments,
the thermal pulse method described herein utilizes a plasma arc
lamp with an argon plasma. The use of a plasma arc lamp with an
argon plasma provides the particular advantage of providing a
significantly increased operating space compared to other thermal
pulse configurations of the art, such as those using a flash lamp,
particularly a xenon flash lamp.
[0086] As indicated above, the divalent metal gallate spinel
structure may be employed as a phosphor. A phosphor is any material
that, when exposed to radiation, emits visible light. The impinging
radiation may be, for example, ultraviolet light (e.g., 254 nm to
288 nm) or a beam of electrons. In one application of the
above-described divalent metal gallate spinel structures, divalent
metal gallate spinel structures including doped divalent metal
gallate spinel structures that emit wavelengths of light within the
red, green, and blue spectra are mixed to provide white light
suitable for efficient solid state lighting. White light is a
mixture of the colors of the visible spectrum. This "visible light"
corresponds to a wavelength range of 400 nm to 700 nm, and a color
range of violet through red.
[0087] In one embodiment, a method of forming a structure for
emitting white light is provided by forming a first phosphor of a
first doped zinc gallate spinel structure that is nucleated by a
fermentation with a thermophilic bacteria and annealing, wherein
the first phosphor emits a first wavelength of red light ranging
from 570 nm to 750 nm. This first phosphor may be formed in
accordance with steps 50-75 of FIG. 4, in which zinc gallate spinel
structure is doped with chromium (Cr), e.g., chromium (Cr.sup.3+),
or europium (Eu), e.g., europium (Eu.sup.3+). The concentration of
the chromium (Cr) dopant and the chromium (Cr.sup.+) dopant source
has been provided above with reference to step 65 of FIG. 4. The
concentration of the europium (Eu) dopant, and the europium
(Eu.sup.3+) dopant source have been described above with reference
to FIG. 4. The annealing conditions applied to the zinc gallate
spinel structures doped with chromium (Cr) and/or europium (Eu)
dopant have been described above with reference to step 75 of FIG.
4.
[0088] In one embodiment, a second phosphor may be formed to mix
with at least the first phosphor in order to provide white light.
The second phosphor may be a second doped zinc gallate spinel
structure that is nucleated by a second fermentation with
thermophilic bacteria and annealing in accordance with steps 50-75
of FIG. 4. The second phosphor may be doped to emit a wavelength of
green light ranging from 495 nm to 570 nm. The zinc gallate spinel
structure that provides the second phosphor may be doped with a
manganese (Mn) dopant, e.g., Mn.sup.2+. The concentration of the
manganese (Mn) dopant and the manganese (Mn.sup.2+) dopant source
have been described above with reference to step 65 of FIG. 4. The
annealing conditions applied to the zinc gallate spinel structures
doped with manganese (Mn) dopant have been described above with
reference to step 75 of FIG. 4.
[0089] In one embodiment, a third phosphor may be formed to mix
with at least one of the first and second phosphor in order to
provide white light. The third phosphor may be a zinc gallate
spinel structure that is nucleated by a fermentation with
thermophilic bacteria in accordance with steps 5-20 of FIG. 1A. The
third phosphor may emit a wavelength of blue light ranging from 400
nm to 495 nm. In some embodiments, the wavelength of light being
emitted from the phosphor that provides the emission of blue light
may be the similar or shifted to a higher wavelength than the
undoped zinc gallate spinel structure by introducing a cobalt
dopant and annealing the zinc gallate spinel structure that has
been doped with cobalt. The concentration of the cobalt (Co) dopant
and the cobalt (Co.sup.2+) dopant source have been described above
with reference to step 65 of FIG. 4. The zinc gallate spinel
structure that has been doped with cobalt (Co) is typically
annealed to provide a wavelength shift within a range of
wavelengths ranging from 400 nm to 495 nm with the maximum peak of
470 nm using the excitation at 254 nm. The annealing conditions
applied to the zinc gallate spinel structures doped with cobalt
(Co) have been described above with reference to step 75 of FIG. 4.
In some embodiments, the cobalt dopant that has been added to the
doped zinc gallate spinel structure increases the intensity of the
emission of blue light of the zinc gallate spinel structure. For
example, a cobalt doped zinc gallate spinel structure may exhibit
an emission of blue light having an increase in intensity ranging
from 180% to 240% when compared to the intensity of emitted blue
light from an undoped zinc gallate spinel structure without
annealing in FIG. 9.
[0090] In some embodiments, a fourth phosphor may also be mixed
with at least one of the first phosphor, the second phosphor and
the third phosphor in order to provide a white light producing
structure. In some embodiments, the fourth phosphor may be used
without mixing with any first, second, or third phosphor to provide
a white light producing structure. In some embodiments, the fourth
phosphor may be a zinc gallate spinel structure that is doped with
dysprosium (Dy), e.g., Dy.sup.3+. The wavelength of light emission
for the dysprosium (Dy) doped zinc gallate spinel may range from
450 nm to 510 nm, 560 nm to 610 nm, 660 nm to 720 nm or 755 nm to
810 nm. The concentration of the dysprosium (Dy) dopant source have
been described above with reference to step 65 of FIG. 4. The zinc
gallate spinel structure that has been doped with dysprosium (Dy)
is typically annealed either to provide a wavelength shift within a
range of wavelengths ranging within .+-.5 nm, .+-.10 nm, .+-.15 nm,
.+-.20 nm, .+-.25 nm, .+-.30 nm, .+-.40 nm, .+-.50 nm or any range
resulting from any two of the foregoing values from the 450 nm to
510 nm, 560 nm to 610 nm, 660 nm to 720 nm or 755 nm to 810 nm or
to provide increased emission. The annealing conditions applied to
the zinc gallate spinel structures doped with dysprosium (Dy) have
been described above with reference to step 75 of FIG. 4.
[0091] The selected combination including at least two of the first
phosphors, the second phosphor, the third phosphor and the fourth
phosphor may be mechanically mixed to provide a mixture in which
the amounts of the selected first, second, third and fourth
phosphor are selected so that the combination of the emitted
wavelengths from the phosphor mixture provides a white light. The
percentage by weight for each of the divalent metal gallate spinel
structures in the mixture of the at least two of the first, second,
third and fourth phosphor may be a range that is selected from the
group of 1% to 100%, 10% to 90%, 20% to 80%, 30% to 70%, 40% to 60%
and 50%. In one embodiment, white light emission can be provided by
a mixture of 50-80% of the first phosphor of red, 15-35% of the
second phosphor of green, and 5-15% of the third phosphor of blue
produce white emission. The mixture may be a homogeneous
distribution of each of the divalent metal gallate spinel
structures that provide the phosphors. Mixing of the at least two
of the first phosphors, the second phosphor, the third phosphor,
and the fourth phosphor may be provided using mechanical means,
such as stirring. The mixture may be fabricated into a design in a
heterogeneous manner laterally or horizontally to provide a
three-dimensional distribution for a specific device
application.
[0092] Although the white light-emitting structure may be a mixture
of divalent metal gallate spinel structures that provides at least
two phosphors that emit different wavelengths of light in a mixed
powder form, embodiments are contemplated in which the white
light-emitting structure further includes the mixture of the
divalent metal gallate spinel structures in a binder, as depicted
in FIG. 5. FIG. 5 depicts an embodiment of a white light-emitting
structure 80 composed of phosphors of zinc gallate spinel
structures and doped zinc gallate spinel structures that are formed
in accordance with the methods described above with reference to
FIGS. 1 and 4.
[0093] Referring to FIG. 5, in some examples, the zinc gallate
spinel structures may be incorporated within a transparent
substrate 81 by mixing a binder with the zinc gallate spinel
structures, wherein the binder provides a matrix of the transparent
substrate 81 and the doped zinc gallate spinel structures provides
a dispersed phase within the transparent substrate 81. The zinc
gallate spinel structures that are contained within the transparent
substrate 81 may include a first zinc gallate spinel structure 82
that is doped with chromium (Cr) or europium (Eu) to provide a red
light emitting phosphor, a second zinc gallate spinel structure 83
that is doped with manganese (Mn) provides a green light emitting
phosphor, and a third zinc gallate spinel structure 84 that
provides a blue light emitting phosphor. The foregoing example
provided in FIG. 5 may also be generalized to any divalent metal
gallate spinel structure.
[0094] In other embodiments, the doped zinc gallate spinel
structures provides a dispersed phase within the transparent
substrate 81. The zinc gallate spinel structures that are contained
within the transparent substrate 81 may include one type of zinc
gallate spinel structure 82 that is doped with dysprosium (Dy) to
provide a white light. In other embodiments, single zinc gallate
spinel structures that are contained within the transparent
substrate 81 may include one type of zinc gallate structure 82 that
is doped with mixed dopants of manganese (Mn), chromium (Cr),
europium (Eu), cobalt (Co), dysprosium (Dy) and combinations
thereof to provide a white light. The foregoing examples may also
be generalized to any divalent metal gallate spinel structure.
[0095] Some methods of incorporating the divalent metal gallate
spinel structure within a transparent substrate include cavity
encapsulation and coating. In some embodiments, cavity
encapsulation includes mixing the divalent metal gallate spinel
structures that provide phosphors with a binder, such as epoxy or
silicon. The mixture is then deposited on a supporting substrate,
such as a glass substrate. In a coating process, the mixed powders
of the divalent metal gallate spinel structures that provide the
red, green, and blue light emitting phosphors are sprayed with a
silicone/binder/solvent combination.
[0096] Referring to FIG. 5, in one embodiment, a blue light
emitting diode/ultraviolet light emitting diode 85 is positioned to
expose the transparent substrate 81 containing the phosphors
provided by the zinc gallate spinel structures 82, 83, 84 to
radiation. In response to the radiation exposure from the blue
light emitting diode/ultraviolet light emitting diode 85, the first
zinc gallate spinel structure 82 emits wavelengths of red light,
the second zinc gallate spinel structure 83 emits wavelengths of
green light and the third zinc gallate spinel structure 84 emits
wavelengths of blue light, wherein the mixture of red, green and
blue wavelengths provide white light 86. In some embodiments, a
beam of electrons may be substituted for the blue light emitting
diode/ultraviolet light emitting diode 85 to provide the radiation
source that is applied to the zinc gallate spinel structures 82,
83, 84. In some embodiments, visible light may be substituted for
the blue light emitting diode/ultraviolet light emitting diode 85
to provide the excitation source that is applied to the zinc
gallate spinel structures 82, 83, 84 that can produce white light
or specific color deviated from white light. Although, the
structure depicted in FIG. 5 includes three different composition
zinc gallate spinel structures 82, 83, 84, the present disclosure
is not limited to only this embodiment, as any number of zinc
gallate spinel structure compositions may be incorporated into the
transparent substrate 81. Further, the selection of the composition
of the wavelength of light does not have to be only white light.
For example, the composition of the zinc gallate spinel structures
that are contained within the transparent substrate may be selected
to provide any visible wavelength of light emission, e.g., blue,
cyan, green, yellow, orange, and red. Embodiments have also been
contemplated in which the composition of the zinc gallate spinel
structures is selected to emit ultraviolet and infrared wavelengths
of light.
[0097] The following examples are provided to further illustrate
the methods and structures of the present disclosure and
demonstrate some advantages that arise therefrom. It is not
intended that the present disclosure be limited to the specific
examples described herein.
Zinc Gallate Spinel Structure Test Samples
[0098] Incubation of fermentative thermophilic bacteria was
initiated in a medium that included 10 mM glucose and 2% (vol)
mid-log growth Thermoanaerobacter sp. TOR-39 at 65.degree. C. The
pH was adjusted to be within the range of 6.5 to 8.5. After a
period of 24 hours, precursor salts equivalent to 2 mM of target
ZnGa.sub.2O.sub.4 were added, as specified in Table 1. More
specifically, the fermentative thermophilic bacteria were incubated
with metal ion precursor, i.e., zinc and gallium precursors, with
doping elements, such as manganese (Mn), cobalt (Co), chromium
(Cr), europium (Eu) and cobalt (Co), with consideration given to
molar fraction as described in Table 1. The total precursor salt
concentration was set to 6 mM.
TABLE-US-00001 TABLE 1 Precursor (salt) solution Sample Substituted
Zn.sup.2+ Ga.sup.3+ Mn.sup.2+ Co.sup.2+ Cr.sup.3+ Eu.sup.3+
Dy.sup.3+ # Target materials element (%) (mM) (mM) (mM) (mM) (mM)
(mM) (mM) 1 ZnGa.sub.2O.sub.4 2 4 2
Zn.sub.0.99Mn.sub.0.01Ga.sub.2O.sub.4 Zn 1% 1.98 4 0.02 3
Zn.sub.0.98Mn.sub.0.02Ga.sub.2O.sub.4 Zn 2% 1.96 4 0.04 4
Zn.sub.0.96Mn.sub.0.04Ga.sub.2O.sub.4 Zn 4% 1.92 4 0.08 5
Zn.sub.0.94Mn.sub.0.06Ga.sub.2O.sub.4 Zn 6% 1.88 4 0.12 6
ZnGa.sub.1.98Mn.sub.0.02O.sub.4 Ga 1% 2 3.96 0.04 7
ZnGa.sub.1.96Mn.sub.0.04O.sub.4 Ga 2% 2 3.92 0.08 8
ZnGa.sub.1.92Mn.sub.0.08O.sub.4 Ga 4% 2 3.84 0.12 9
ZnGa.sub.1.88Mn.sub.0.12O.sub.4 Ga 6% 2 3.76 0.24 10
Zn.sub.0.99Co.sub.0.01Ga.sub.2O.sub.4 Zn 1% 1.98 4 0.02 11
Zn.sub.0.98Co.sub.0.02Ga.sub.2O.sub.4 Zn 2% 1.96 4 0.04 12
Zn.sub.0.96Co.sub.0.04Ga.sub.2O.sub.4 Zn 4% 1.92 4 0.08 13
Zn.sub.0.94Co.sub.0.06Ga.sub.2O.sub.4 Zn 6% 1.88 4 0.12 14
ZnGa.sub.1.98Cr.sub.0.02O.sub.4 Ga 1% 2 3.96 0.04 15
ZnGa.sub.1.96Cr.sub.0.04O.sub.4 Ga 2% 2 3.92 0.08 16
ZnGa.sub.1.92Cr.sub.0.08O.sub.4 Ga 4% 2 3.84 0.16 17
ZnGa.sub.1.88Cr.sub.0.12O.sub.4 Ga 6% 2 3.76 0.24 18
ZnGa.sub.1.80Cr.sub.0.20O.sub.4 Ga 10% 2 3.60 0.40 19
ZnGa.sub.1.98Eu.sub.0.02O.sub.4 Ga 1% 2 3.96 0.04 20
ZnGa.sub.1.96Eu.sub.0.04O.sub.4 Ga 2% 2 3.92 0.08 21
ZnGa.sub.1.92Eu.sub.0.08O.sub.4 Ga 4% 2 3.84 0.16 22
ZnGa.sub.1.88Eu.sub.0.12O.sub.4 Ga 6% 2 3.76 0.24 23
ZnGa.sub.1.80Eu.sub.0.20O.sub.4 Ga 10% 2 3.60 0.40 24
ZnGa.sub.1.98Dy.sub.0.02O.sub.4 Ga 1% 2 3.96 0.04 25
ZnGa.sub.1.94Dy.sub.0.04O.sub.4 Ga 3% 2 3.88 0.12 26
ZnGa.sub.1.88Dy.sub.0.08O.sub.4 Ga 5% 2 3.80 0.20
[0099] Final products of pure and metal doped zinc gallates were
produced in batch sizes scaled from 10 milliliter (ml) in pressure
tubes to 1 liter (L) in culture bottles. After two weeks, solid
precipitated phosphors of zinc gallate spinel structures were
harvested washed and used for characterization. In some instances,
samples were processed through centrifugation, washing, and stored
by mixing with methanol. The samples were then characterized using
X-ray diffraction. Following characterization with X-ray
diffraction, the doped zinc gallate spinel structures, i.e., sample
numbers 2-26, were sintered at a temperature of 900.degree. C. for
a time period of 30 minutes in air and/or 30 min in inert gas if
needed.
Flourescence and X-Ray Diffraction Patterns of Pure Zinc Gallate
Structures
[0100] FIG. 6 is plot of the fluorescence of a pure zinc gallate
spinel structure that exhibited an emission of light within the
blue region of wavelengths. The composition of the pure zinc
gallate spinel structure that provided data line 90, which is
plotted in FIG. 6, is listed Table 1 and had a target composition
of ZnGa.sub.2O.sub.4. The pure zinc gallate structure exhibited a
peak fluorescence at a wavelength proximate to 430 nm in response
to the application of UV light having a wavelength of 254 nm. FIG.
7 is an X-ray diffraction pattern taken from a pure zinc gallate
spinel structure having the composition of sample 1 listed in Table
1.
Flourescence and X-Ray Diffraction Patterns of Zinc Gallate
Structures Doped with Cobalt
[0101] FIG. 8 is a plot of X-ray diffraction lines confirming that
sample numbers 10-13 in Table 1 had a spinel crystal structure.
Sample numbers 10-13 in Table 1 were a zinc gallate spinel
structure that was doped with cobalt so that the cobalt was a
substitutional dopant for zinc. Diffraction line 95 is the X-ray
diffraction line taken from sample number 10 of Table 1, wherein
the zinc gallate spinel structure was produced from the precursor
solution equal to the target composition of
Zn.sub.0.99Co.sub.0.01Ga.sub.2O.sub.4. Diffraction line 100 is the
X-ray diffraction line taken from sample number 11 of Table 1,
wherein the zinc gallate spinel structure was produced from the
precursor solution equal to the target composition of
Zn.sub.0.98Co.sub.0.02Ga.sub.2O.sub.4. Diffraction line 105 is the
X-ray diffraction line taken from sample number 12 of Table 1,
wherein the zinc gallate spinel structure was produced from the
precursor solution equal to the target composition of
Zn.sub.0.96Co.sub.0.04Ga.sub.2O.sub.4. Diffraction line 110 is the
X-ray diffraction line taken from sample number 13 of Table 1,
wherein the zinc gallate spinel structure was produced from the
precursor solution equal to the target composition of
Zn.sub.0.94Co.sub.0.06Ga.sub.2O.sub.4.
[0102] FIG. 9 is a plot of the fluorescence from zinc gallate
spinel structures doped with cobalt in response to the application
of ultraviolet light having a wavelength of 254 nm. FIG. 9 depicts
emission of wavelengths from the zinc gallate spinel structures
doped with cobalt and pure zinc gallate spinel structures within
the blue light spectrum. The zinc gallate spinel structures that
provided the fluorescence plotted in FIG. 9 were doped zinc gallate
spinel structures, in which cobalt was a substitution dopant with
the zinc in the doped zinc gallate spinel structure. Data line 115
is a plot of the photoluminescence (PL) intensity measured from
sample number 10 of Table 1, which was a zinc gallate spinel
structure produced from the precursor solution equal to the target
composition of Zn.sub.0.99 CO.sub.0.01Ga.sub.2O.sub.4 (hereafter
referred to as the zinc gallate spinel structure doped with 1%
cobalt substituted for zinc). Data line 120 is a plot of the
photoluminescence (PL) intensity measured from sample number 11 of
Table 1 having a zinc gallate spinel structure produced from the
precursor solution equal to the target composition of Zn.sub.0.98
CO.sub.0.02Ga.sub.2O.sub.4 (hereafter referred to as the zinc
gallate spinel structure doped with 2% cobalt substituted for
zinc). Data line 125 is a plot of the photoluminescence (PL)
intensity measured from sample number 12 of Table 1 having a zinc
gallate spinel structure produced from the precursor solution equal
to the target composition of Zn.sub.0.96Co.sub.0.04Ga.sub.2O.sub.4
(hereafter referred to as the zinc gallate spinel structure doped
with 4% cobalt substituted for zinc). Data line 130 is a plot of
the photoluminescence (PL) intensity measured from sample number 13
of Table 1 having a zinc gallate spinel structure produced from the
precursor solution equal to the target composition of
Zn.sub.0.94Co.sub.0.06Ga.sub.2O.sub.4 (hereafter referred to as the
zinc gallate spinel structure doped with 6% cobalt substituted for
zinc). Data line 135 is a plot of the photoluminescence (PL)
intensity measured from sample number 1 of Table 1, which is a pure
undoped zinc gallate structure having a zinc gallate spinel
structure produced from the precursor solution equal to the target
composition of ZnGa.sub.2O.sub.4. The pure undoped zinc gallate
structures were not sintered. The peak wavelength of light emitted
by the cobalt doped zinc gallate structures in response to the
application of UV light having a wavelength of 254 nm that provided
data lines 115, 120, 125, 130, 135 exhibited a peak fluorescence at
a wavelength that was proximate to 430 nm.
[0103] The greatest photoluminescence (PL) intensity measured from
the cobalt doped zinc gallate structures in response to the
application of the ultraviolet light having the 254 nm wavelength
was measured from the zinc gallate spinel structure doped with 1%
cobalt substituted for zinc, as indicated by data line 115,
followed by the zinc gallate spinel structure doped with 2% cobalt
substituted for zinc, as indicated by data line 120. The cobalt
doped zinc gallate spinel structures having the greater
concentration of cobalt dopant, e.g., the zinc gallate spinel
structure doped with 4% cobalt substituted for zinc depicted by
data line 125 and the zinc gallate structure doped with 6% cobalt
substituted for zinc depicted by data line 130, had a lower
photoluminescence (PL) intensity. The pure undoped zinc gallate
structure that provided data line 135 had a lower photoluminescence
(PL) intensity when compared to the samples that were doped with
cobalt as indicated by FIG. 9.
[0104] FIG. 10 is a plot of the fluorescence from zinc gallate
spinel structure doped with cobalt in response to the application
of ultraviolet light having a wavelength of 288 nm. FIG. 10 depicts
emission of wavelengths from the zinc gallate spinel structures
doped with cobalt and pure zinc gallate spinel structures within
the blue light spectrum. In FIG. 10, the cobalt is a substitution
dopant with zinc in the doped zinc gallate spinel structure. Data
line 140 is a plot of the photoluminescence (PL) intensity measured
sample number 10 of Table 1, which was a zinc gallate spinel
structure produced from the precursor solution equal to the target
composition of Zn.sub.0.99 Co.sub.0.01Ga.sub.2O.sub.4 (hereafter
referred to as the zinc gallate spinel structure doped with 1%
cobalt substituted for zinc). Data line 145 is a plot of the
photoluminescence (PL) intensity measured from sample number 11 of
Table 1 having a zinc gallate spinel structure produced from the
precursor solution equal to the target composition of
Zn.sub.0.98Co.sub.0.02Ga.sub.2O.sub.4 (hereafter referred to as the
zinc gallate spinel structure doped with 2% cobalt substituted for
zinc). Data line 150 is a plot of the photoluminescence (PL)
intensity measured from sample number 12 of Table 1 having a zinc
gallate spinel structure produced from the precursor solution equal
to the target composition of Zn.sub.0.96Co.sub.0.04Ga.sub.2O.sub.4
(hereafter referred to as the zinc gallate spinel structure doped
with 4% cobalt substituted for zinc). Data line 155 is a plot of
the photoluminescence (PL) intensity measured from sample number 13
of Table 1 having a zinc gallate spinel structure produced from the
precursor solution equal to the target composition of
Zn.sub.0.94Co.sub.0.06Ga.sub.2O.sub.4 (hereafter referred to as the
zinc gallate spinel structure doped with 6% cobalt substituted for
zinc). Data line 160 is a plot of the photoluminescence (PL)
intensity measured from sample number 1 of Table 1, which is a pure
undoped zinc gallate structure produced from the precursor solution
equal to the target composition of ZnGa.sub.2O.sub.4. The pure
undoped zinc gallate structures that provided data line 160 were
not sintered. The peak wavelength of light emitted by the cobalt
doped zinc gallate structures in response to the application of UV
light having a wavelength of 288 nm that provided data lines 140,
145, 150, 155, 160 exhibited a peak fluorescence at a wavelength
that was proximate to 430 nm.
[0105] The greatest photoluminescence (PL) intensity by the cobalt
doped zinc gallate structures in response to the application of the
ultraviolet light having the 288 nm wavelength was measured from
the zinc gallate spinel structure doped with 1% cobalt substituted
for zinc, as indicated by data line 140, followed by the zinc
gallate spinel structure doped with 2% cobalt substituted for zinc,
as indicated by data line 145. The cobalt doped zinc gallate spinel
structures having the greater concentration of cobalt dopant, e.g.,
the zinc gallate spinel structure doped with 4% cobalt substituted
for zinc depicted by data line 150, and the zinc gallate spinel
structure doped with 6% cobalt substituted for zinc depicted by
data line 155, had a lower photoluminescence (PL) intensity. The
pure undoped zinc gallate structure that provided data line 160 had
a lower photoluminescence (PL) intensity when compared to the
samples that were doped with cobalt as indicated by FIG. 10.
Flourescence and X-Ray Diffraction Patterns of Zinc Gallate
Structures Doped with Manganese
[0106] FIG. 11 is a plot of X-ray diffraction lines confirming that
sample numbers 2-5 in Table 1 had a spinel crystal structure.
Sample numbers 2-5 where zinc gallate spinel structures that were
doped with manganese so that the manganese is a substitutional
dopant for zinc. Diffraction line 165 is the X-ray diffraction line
taken from sample number 2 of Table 1, which was produced from the
precursor solution equal to the target composition of
Zn.sub.0.99Mn.sub.0.01Ga.sub.2O.sub.4. Diffraction line 170 is the
X-ray diffraction line taken from sample number 3 of Table 1, which
was produced from the precursor solution equal to the target
composition of Zn.sub.0.98Mn.sub.0.02Ga.sub.2O.sub.4. Diffraction
line 175 is the X-ray diffraction line taken from sample number 4
of Table 1, which was produced from the precursor solution equal to
the target composition of Zn.sub.0.96Mn.sub.0.04Ga.sub.2O.sub.4.
Diffraction line 180 is the X-ray diffraction line taken from
sample number 5 of Table 1, which was produced from the precursor
solution equal to the target composition of
Zn.sub.0.94Mn.sub.0.06Ga.sub.2O.sub.4.
[0107] FIG. 12 is a plot of the fluorescence from zinc gallate
spinel structure doped with manganese in response to the
application of ultraviolet light having a wavelength of 288 nm, in
which the manganese was a substitutional dopant for the zinc in the
zinc gallate spinel structure. FIG. 12 depicts emission of
wavelengths from the zinc gallate spinel structures doped with
manganese within the green light spectrum. In FIG. 12, the
manganese is a substitution dopant with zinc in the doped zinc
gallate spinel structure. Data line 185 is a plot of the
photoluminescence (PL) intensity measured sample number 2 of Table
1, which was a zinc gallate spinel structure produced from the
precursor solution equal to the target composition of
Zn.sub.0.99Mn.sub.0.01Ga.sub.2O.sub.4 (hereafter referred to as a
zinc gallate structure doped with 1% manganese substituted for
zinc). Data line 190 is a plot of the photoluminescence (PL)
intensity measured from sample number 3 of Table 1, which was
produced from the precursor solution equal to the target
composition of Zn.sub.0.98Mn.sub.0.02Ga.sub.2O.sub.4 (hereafter
referred to as a zinc gallate structure doped with 2% manganese
substituted for zinc). Data line 195 is a plot of the
photoluminescence (PL) intensity measured from sample number 4 of
Table 1, which was produced from the precursor solution equal to
the target composition of Zn.sub.0.96Mn.sub.0.04Ga.sub.2O.sub.4
(hereafter referred to as a zinc gallate structure doped with 4%
manganese substituted for zinc). Data line 200 is a plot of the
photoluminescence (PL) intensity measured from sample number 5 of
Table 1, which was produced from the precursor solution equal to
the target composition of Zn.sub.0.94Mn.sub.0.06Ga.sub.2O.sub.4
(hereafter referred to as a zinc gallate structure doped with 6%
manganese substituted for zinc). Data line 205 is a plot of the
photoluminescence (PL) intensity measured from sample number 5 of
Table 1, which is a pure undoped zinc gallate structure produced
from the precursor solution equal to the target composition of
ZnGa.sub.2O.sub.4. The pure undoped zinc gallate structures that
provided data line 205 were not sintered. The peak wavelength of
light emitted by the manganese doped zinc gallate structures in
response to the application of UV light having a wavelength of 288
nm that provided data lines 185, 190, 195, and 200 exhibited a peak
fluorescence at a wavelength that was proximate to 510 nm. In
comparison, the undoped zinc gallate spinel structure that provided
data line 205 exhibited a peak fluorescence at a wavelength that
was proximate to 450 nm.
[0108] The greatest photoluminescence (PL) intensity by the doped
zinc gallate structures having manganese substituted for zinc in
response to the application of the ultraviolet light having the 288
nm wavelength was measured from the doped zinc gallate spinel
structure with 6% manganese substituted for zinc, as indicated by
data line 200, and the manganese doped zinc gallate spinel
structure with 4% manganese substituted for zinc, as indicated by
data line 195. The manganese doped zinc gallate spinel structures
having the lower concentration of dopant, e.g., the doped zinc
gallate structure with 2% manganese substituted for zinc depicted
by data line 190 and the doped zinc gallate structure with 1%
manganese substituted for zinc depicted by data line 185, had a
lower photoluminescence (PL) intensity than the doped zinc gallate
structures having the higher concentrations of manganese
substituted for zinc. The pure undoped zinc gallate structure
identified by data line 205 had the lowest photoluminescence (PL)
intensity.
[0109] FIG. 13 is a plot of X-ray diffraction lines confirming that
sample numbers 6-9 in Table 1 had a spinel crystal structure.
Sample numbers 6-9 were zinc gallate spinel structures that were
doped with manganese so that the manganese was a substitutional
dopant for gallium. Diffraction line 210 is the X-ray diffraction
line taken from sample number 6 of Table 1, which was produced from
the precursor solution equal to the target composition of
ZnGa.sub.1.98Mn.sub.0.02O.sub.4. Diffraction line 215 is the X-ray
diffraction line taken from sample number 7 of Table 1, which was
produced from the precursor solution equal to the target
composition of ZnGa.sub.1.96Mn.sub.0.04O.sub.4. Diffraction line
220 is the X-ray diffraction line taken from sample number 8 of
Table 1, which was produced from the precursor solution equal to
the target composition of ZnGa.sub.1.92Mn.sub.0.08O.sub.4.
Diffraction line 225 is the X-ray diffraction line taken from
sample number 9 of Table 1, which was produced from the precursor
solution equal to the target composition of
ZnGa.sub.1.88Mn.sub.0.12O.sub.4.
[0110] FIG. 14 depicts emission of wavelengths measured from the
zinc gallate spinel structures doped with manganese within the
green light spectrum. In FIG. 14, the manganese was a substitution
dopant with gallium in the doped zinc gallate spinel structure.
Data line 230 is a plot of the photoluminescence (PL) intensity
measured sample number 6 of Table 1, which was a zinc gallate
spinel structure produced from the precursor solution equal to the
target composition of ZnGa.sub.1.98Mn.sub.0.02O.sub.4 (hereafter
referred to as a zinc gallate structure doped with 1% manganese
substituted for gallium). Data line 235 is a plot of the
photoluminescence (PL) intensity measured from sample number 7 of
Table 1, which was a zinc gallate spinel structure produced from
the precursor solution equal to the target composition of
(hereafter referred to as a zinc gallate structure doped with 2%
manganese substituted for gallium). Data line 240 is a plot of the
photoluminescence (PL) intensity measured from sample number 4 of
Table 1, which was a zinc gallate spinel structure produced from
the precursor solution equal to the target composition of
ZnGa.sub.1.92Mn.sub.0.08O.sub.4 (hereafter referred to as a zinc
gallate structure doped with 4% manganese substituted for gallium).
Data line 245 is a plot of the photoluminescence (PL) intensity
measured from sample number 5 of Table 1, which was a zinc gallate
spinel structure produced from the precursor solution equal to the
target composition of ZnGa.sub.1.88Mn.sub.0.12O.sub.4 (hereafter
referred to as a zinc gallate structure doped with 6% manganese
substituted for gallium). Data line 250 is a plot of the
photoluminescence (PL) intensity measured from sample number 5 of
Table 1, which is a pure undoped zinc gallate structure produced
from the precursor solution equal to the target composition of
ZnGa.sub.2O.sub.4. The pure undoped zinc gallate structures that
provided data line 250 were not sintered. The peak wavelength of
light emitted by the manganese doped zinc gallate structures, in
which manganese was substituted with gallium, in response to the
application of UV light having a wavelength of 288 nm that provided
data lines 230, 235, 240, and 245 exhibited a peak fluorescence at
a wavelength that was proximate to 510 nm. In comparison, the
undoped zinc gallate spinel structure that provided data line 250
exhibited a peak fluorescence at a wavelength that was proximate to
450 nm.
[0111] The greatest photoluminescence (PL) intensity by the doped
zinc gallate structures having manganese substituted for gallium in
response to the application of the ultraviolet light having the 288
nm wavelength was measured from the zinc gallate structure doped
with 4% manganese substituted for gallium, as indicated by data
line 240, and the zinc gallate structure doped with 6% manganese
substituted for gallium, as indicated by data line 245. The
manganese doped zinc gallate spinel structures having the lower
concentration of dopant, e.g., the zinc gallate structure doped
with 2% manganese substituted for gallium depicted by data line 230
and the zinc gallate structure doped with 1% manganese substituted
for gallium depicted by data line 235, had a lower
photoluminescence (PL) intensity than the doped zinc gallate
structures having the higher concentrations of manganese
substituted for gallium. The pure undoped zinc gallate structure
identified by data line 205 had a lower photoluminescence (PL)
intensity than the doped zinc gallate structures with the exception
of the zinc gallate structure doped with 1% manganese substituted
for gallium.
Flourescence and X-Ray Diffraction Patterns of Zinc Gallate
Structures Doped with Chromium
[0112] FIG. 15 is a plot of X-ray diffraction lines confirming that
sample numbers 14-18 in Table 1 had a spinel crystal structure.
Sample numbers 14-18 were zinc gallate spinel structures that were
doped with chromium so that the chromium was a substitutional
dopant for gallium. Diffraction line 255 is the X-ray diffraction
line taken from sample number 14 of Table 1, which was produced
from the precursor solution equal to the target composition of
ZnGa.sub.1.98Cr.sub.0.02O.sub.4. Diffraction line 260 is the X-ray
diffraction line taken from sample number 15 of Table 1, which was
produced from the precursor solution equal to the target
composition of ZnGa.sub.1.96Cr.sub.0.04O.sub.4. Diffraction line
265 is the X-ray diffraction line taken from sample number 16 of
Table 1, which was produced from the precursor solution equal to
the target composition of ZnGa.sub.1.92Cr.sub.0.08O.sub.4.
Diffraction line 270 is the X-ray diffraction line taken from
sample number 17 of Table 1, which was produced from the precursor
solution equal to the target composition of
ZnGa.sub.1.88Cr.sub.0.12O.sub.4. Diffraction line 275 is the X-ray
diffraction line taken from sample number 18 of Table 1, which was
produced from the precursor solution equal to the target
composition of ZnGa.sub.1.80Cr.sub.0.20O.sub.4.
[0113] FIG. 16 is a plot of the fluorescence from zinc gallate
spinel structure doped with chromium in response to the application
of ultraviolet light having a wavelength of 288 nm, in which the
chromium was a substitutional dopant for the zinc in the zinc
gallate spinel structure. FIG. 16 depicts emission of wavelengths
from the zinc gallate spinel structures doped with chromium within
the red light spectrum. Data line 280 is a plot of the
photoluminescence (PL) intensity measured sample number 14 of Table
1, which was a zinc gallate spinel structure produced from the
precursor solution equal to the target composition of
ZnGa.sub.1.98Cr.sub.0.02O.sub.4 (hereafter referred to as a zinc
gallate structure doped with 1% chromium substituted for gallium).
Data line 285 is a plot of the photoluminescence (PL) intensity
measured from sample number 15 of Table 1 produced from the
precursor solution equal to the target composition of
ZnGa.sub.1.96Cr.sub.0.04O.sub.4 (hereafter referred to as a zinc
gallate structure doped with 2% chromium substituted for gallium).
Data line 290 is a plot of the photoluminescence (PL) intensity
measured from sample number 16 of Table 1 produced from the
precursor solution equal to the target composition of
ZnGa.sub.1.92Cr.sub.0.08O.sub.4 (hereafter referred to as a zinc
gallate structure doped with 4% chromium substituted for gallium).
Data line 295 is a plot of the photoluminescence (PL) intensity
measured from sample number 17 of Table 1 produced from the
precursor solution equal to the target composition of
ZnGa.sub.1.88Cr.sub.0.12O.sub.4 (hereafter referred to as a zinc
gallate structure doped with 6% chromium substituted for gallium).
Data line 300 is a plot of the photoluminescence (PL) intensity
measured from sample number 10 of Table 1 produced from the
precursor solution equal to the target composition of
ZnGa.sub.1.80Cr.sub.0.20O.sub.4 (hereafter referred to as a zinc
gallate structure doped with 10% chromium substituted for gallium).
The peak wavelength of light emitted by the chromium doped zinc
gallate structures in response to the application of UV light
having a wavelength of 288, such as the peak wavelength illustrated
by data lines 280 and 285, was proximate to 700 nm.
[0114] The greatest photoluminescence (PL) intensity by the doped
zinc gallate structures having chromium substituted for gallium in
response to the application of the ultraviolet light having the 288
nm wavelength was measured from the zinc gallate spinel structure
doped with 1% chromium substituted for gallium, as indicated by
data line 280, and zinc gallate spinel structure doped with 2%
chromium substituted for gallium, as indicated by data line 285.
The chromium doped zinc gallate spinel structures having greater
concentrations of dopant, e.g., the zinc gallate structure doped
with 4% chromium substituted for gallium depicted by data line 290,
the zinc gallate structure doped with 6% chromium substituted for
gallium depicted by data line 295, and the doped zinc gallate
structure with 10% chromium substituted for gallium depicted by
data line 300 did not show distinct emission peak in the red
region.
Flourescence and X-Ray Diffraction Patterns of Zinc Gallate
Structures Doped with Europium
[0115] FIG. 17 is a plot of X-ray diffraction lines confirming that
sample numbers 19-23 in Table 1 had a spinel crystal structure.
Sample numbers 19-23 were zinc gallate spinel structure that were
doped with europium so that the europium was a substitutional
dopant for gallium. Diffraction line 310 is the X-ray diffraction
line taken from sample number 19 of Table 1, which was produced
from the precursor solution equal to the target composition of
ZnGa.sub.1.98Eu.sub.0.02O.sub.4. Diffraction line 315 is the X-ray
diffraction line taken from sample number 20 of Table 1, which was
produced from the precursor solution equal to the target
composition of ZnGa.sub.1.96Eu.sub.0.04O.sub.4. Diffraction line
320 is the X-ray diffraction line taken from sample number 21 of
Table 1, which was produced from the precursor solution equal to
the target composition of ZnGa.sub.1.92Eu.sub.0.08O.sub.4.
Diffraction line 325 is the X-ray diffraction line taken from
sample number 22 of Table 1, which was produced from the precursor
solution equal to the target composition of
ZnGa.sub.1.88Eu.sub.0.12O.sub.4. Diffraction line 330 is the X-ray
diffraction line taken from sample number 23 of Table 1, which was
produced from the precursor solution equal to the target
composition of ZnGa.sub.1.80Eu.sub.0.20O.sub.4.
[0116] FIG. 18 is a plot of the fluorescence from zinc gallate
spinel structure doped with europium in response to the application
of ultraviolet light having a wavelength of 288 nm, in which the
europium was a substitutional dopant for the gallium in the zinc
gallate spinel structure. FIG. 18 depicts emission of wavelengths
from the zinc gallate spinel structures doped with europium within
the red light spectrum. Data line 335 is a plot of the
photoluminescence (PL) intensity measured from sample number 19 of
Table 1, which was a zinc gallate spinel structure produced from
the precursor solution equal to the target composition of to
ZnGa.sub.1.98Eu.sub.0.02O.sub.4 (hereafter referred to as a zinc
gallate structure doped with 1% europium substituted for gallium).
Data line 340 is a plot of the photoluminescence (PL) intensity
measured from sample number 20 of Table 1 produced from the
precursor solution equal to the target composition of
ZnGa.sub.1.96Eu.sub.0.04O.sub.4 (hereafter referred to as a zinc
gallate structure doped with 2% europium substituted for gallium).
Data line 345 is a plot of the photoluminescence (PL) intensity
measured from sample number 21 of Table 1 produced from the
precursor solution equal to the target composition of
ZnGa.sub.1.92Eu.sub.0.08O.sub.4 (hereafter referred to as a zinc
gallate structure doped with 4% europium substituted for gallium).
Data line 350 is a plot of the photoluminescence (PL) intensity
measured from sample number 22 of Table 1 produced from the
precursor solution equal to the target composition of
ZnGa.sub.1.88Cr.sub.0.12O.sub.4 (hereafter referred to as a zinc
gallate structure doped with 6% europium substituted for gallium).
Data line 300 is a plot of the photoluminescence (PL) intensity
measured from sample number 23 of Table 1 produced from the
precursor solution equal to the target composition of
ZnGa.sub.1.80Eu.sub.0.20O.sub.4 (hereafter referred to as a zinc
gallate structure doped with 10% europium substituted for gallium).
The peak wavelength of light emitted by the chromium doped zinc
gallate structures in response to the application of UV light
having a wavelength of 288, such as the peak wavelength illustrated
by data lines 345, 350 and 355, was proximate to 625 nm.
[0117] The greatest photoluminescence (PL) intensity by the doped
zinc gallate structures having europium substituted for gallium in
response to the application of the ultraviolet light having the 288
nm wavelength was measured from the doped zinc gallate spinel
structure with 6% europium substituted for gallium, as indicated by
data line 350, and doped zinc gallate spinel structure with 4%
europium substituted for gallium, as indicated by data line 345.
Following the intensity of the doped zinc gallate spinel structure
with 4% europium substituted for gallium, the next highest
intensity was measured from doped zinc gallate spinel structure
with 10% europium substituted for gallium, as indicated by data
line 355. The europium doped zinc gallate spinel structures having
concentrations of dopant less than 4%, such as the doped zinc
gallate structure with 2% europium substituted for gallium depicted
by data line 340 and the doped zinc gallate structure with 1%
europium substituted for gallium depicted by data line 330, had a
lower photoluminescence (PL) intensity than the doped zinc gallate
structures having concentrations of dopant greater than 4%. A
second peak wavelength of light emission at approximately 450 nm
was measured from each of the europium doped zinc gallate spinel
structures, which was attributed to the wavelength of light emitted
from the host material, i.e., undoped zinc gallate structure.
Flourescence of a Mixture of Doped Zinc Gallate Structures Doped to
Produce White Light
[0118] FIG. 19 is a plot of the fluorescence from a mixture of
doped zinc gallate spinel structures in response to the application
of ultraviolet light having a wavelength of 254 nm. The mixture of
doped zinc gallate spinel structures included a manganese doped
zinc gallate structure having a target composition equal to sample
number 4, i.e., Zn.sub.0.96Mn.sub.0.04Ga.sub.2O.sub.4, of Table 1,
a chromium doped zinc gallate spinel structure having a target
composition equal to sample number 14, i.e., Zn
Ga.sub.1.98Cr.sub.0.02O.sub.4, of Table 1, and a cobalt doped zinc
gallate spinel structure having a composition equal to sample
number 10, i.e., Zn.sub.0.99Co.sub.0.01Ga.sub.2O.sub.4, of Table 1.
The mixture included 50 wt. % cobalt doped zinc gallate spinel
structure, 30 wt. % manganese doped zinc gallate structure, and 20
wt. % chromium doped zinc gallate spinel structure. The mixture of
doped zinc gallate spinel structures emitted white light in
response to the application of ultraviolet light having a
wavelength of 254 nm. Referring to FIG. 19, the wavelength peak at
approximately 475 nm was provide by the cobalt doped zinc gallate
spinel structure portion of the mixture, the wavelength peak at
approximately 510 nm was provided by the manganese doped zinc
gallate structure portion of the mixture, and the wavelength peak
at approximately 700 nm was provided by the chromium doped zinc
gallate spinel structure portion of the mixture.
Preparation and Flourescence of a Copper Gallate
(CuGa.sub.2O.sub.4)
[0119] Copper gallate nanoparticles were microbially produced in a
manner analogous to the above-described process for the production
of zinc gallate nanoparticles. In the process, 2 mM of a copper
salt and 4 mM of a gallium-containing salt were contacted with
bacteria to produce copper gallate nanoparticles of .about.5 nm. A
relatively larger amount of elemental copper (Cu) impurity having a
size of around 90 nm was also observed. FIG. 20 shows the X-ray
diffraction pattern for the copper gallate spinel structures. The
X-ray diffraction pattern shows the presence of copper gallate and
elemental copper.
[0120] The particular embodiments disclosed above are illustrative
only, as the invention may be modified and practiced in different
but equivalent manners apparent to those skilled in the art having
the benefit of the teachings herein. Furthermore, no limitations
are intended to the details of construction or design herein shown,
other than as described in the claims below. It is therefore
evident that the particular embodiments disclosed above may be
altered or modified and all such variations are considered within
the scope and spirit of the invention. Accordingly, the protection
sought herein is as set forth in the claims below.
* * * * *